Written by Grant Maloy Smith, the data acquisition expert

In this article we will discuss how voltage is measured with respect to Data Acquisition (DAQ) applications today, with enough detail so that you will:

  • See which voltage sensors and transducers are available today
  • Learn the basics of accurate voltage measurement
  • Understand how various sensors are applied in voltage measurement applications

Are you ready to get started? Let’s go!

What Is Voltage?

Voltage is the difference in electrical potential between two points. It is sometimes also called tension or pressure, because of the analogy between water and electricity. 

Think about a closed system of water pipes which includes a pump. The pump drives the water around and around the pipes, creating a difference in pressure that drives the water. This pressure pushing the water allows it to do work, such as turning a turbine, for example.

Relationship between voltage, current, and resistance

The relationship between voltage, current, and resistance in a circuit

In this analogy, water represents electricity. The pump represents a power supply. The pressure that the power supply creates in the circuit is the voltage potential, and the rate at which the water moves represents the current.

But let’s stay focused on voltage in this article.

AC Voltage Vs. DC Voltage

Voltage can be either DC or AC, depending on the current that is carrying it. In DC systems, the current never changes direction. It is unidirectional, i.e., it does not change polarity.

But in AC systems, the current alternates directions, crossing 0V in a positive direction, then turning around and crossing 0V again in a negative direction. You can see both DC and AC voltage (and current) represented in the graphs below:

DC circuits (left) versus AC circuits (right)
DC circuits (left) versus AC circuits (right)

The most well-known sources of DC voltage are the common AAA battery or the much bigger one that starts (or even powers!) your car. The most well-known source of AC voltage is the 120 VAC or 230 VAC that powers our homes and businesses.

The Terminology of Voltage Measurement

You may have heard terms like “single-ended referenced,” "single-ended, non-referenced” and “differential” and wondered what they really meant in terms of making voltage measurements. Well, it’s all about the reference point. Remember that right at the beginning of this article we established that voltage is the electrical potential difference between two points.

Single-ended Measurements

Single-ended measurements are those that are made with respect to the ground. The signal is carried only on the positive wire, and the other wire is referenced to the ground. But who provides this ground? 

If the measuring instrument provides the ground reference, then the measurement is classified as “referenced, single-ended.” This is often abbreviated as RSE.

Example of a referenced single-ended measurement (RSE)
Example of a referenced single-ended measurement (RSE)

On the other hand, if the signal itself provides the ground reference, then the measurement is classified as “non-referenced, single-ended”, abbreviated as NRSE.

Example of a non-referenced single-ended measurement (NRSE)
Example of a non-referenced single-ended measurement (NRSE)

Differential Measurements

If we ignore the ground and measure between two points in a circuit, we are making a differential measurement. It’s called differential because we are measuring the DIFFERENCE between these two points. We’re really measuring two signals instead of one in a single-ended scenario. Each differential channel really has two preamps inside it, and these inputs are floating with respect to the ground.

Example of a differential (DIFF) measurement
Example of a differential (DIFF) measurement

Learn more about Dewesoft and voltage/current measurement:

Dewesoft PRO Training > Voltage Measurement

Dewesoft PRO Training > Current Measurement

Floating Signal Sources

You may also hear about a signal source being a “floating” one. This simply means that it is not directly referenced to the ground. A common example of such a source would be a battery. In the case of measuring from the outputs of floating signal sources, the measurement system needs to provide the ground reference. 

What Do Terms Like Average, RMS, Peak-to-Peak Mean?

Voltage can be quantified in several ways. Let’s take a look at each of these common terms and what it means.

Visualising peak, ave, RMS terms for a sinusoidal waveform
Visualizing peak, ave, RMS terms for a sinusoidal waveform

The Average voltage (VAV) is, as the name already states, the average value during one period. For pure sinusoidal signals, the average will be zero, because the amount of current in the first positive half of the waveform is equal to the current in the negative half cycle. These currents cancel each other out resulting in zero. So taking just one half of a cycle we can define the average by taking the peak the peak (max) value and multiply it by 0.637.

The RMS voltage (root-mean-square aka VRMS) is the square root of the arithmetic mean of the squared function values that define the continuous waveform. A common way to calculate RMS is to multiply the peak value by 0.707. RMS is the most common way to express AC voltages.

The Peak voltage (VPK or VMAX) describes the highest voltage within one period.

The Peak-to-peak voltage (VPK) defines the entire amplitude of the positive and negative peaks within one period. 

Crest factor is a ratio of the maximum peak values divided by the RMS value of an AC waveform. Since DC voltage levels and square waves don’t have peaks, they have a crest factor of 1, where a pure sine wave has a crest factor of 1.414.

Please note that in most measuring systems, the average, RMS, peak, and crest factor values are typically calculated over a period of time, usually a subset of the data acquisition system’s selected sample rate. This is a very useful way of presenting these values.

For example, in Dewesoft X data acquisition software, the user can select any of these values and have them calculated at a divisor of the selected sample rate. Here is an example of the setup screen, where you can select which statistical values you’d like to display/record:

Basic statistics math setup screen in the Dewesoft X data acquisition softwareDewesoft X basic statistics setup screen

1. Input Under the Input group, you can select desired input channels for which you want to calculate desired statistics. The statistics support multiple input channels.
2. Output channels Here it can be selected which statistics need to be calculated. Those will be then shown as separate output channels. 
3. Calculation type In the Calculation type group, you can define parameters for the calculation.
4. Output The output area offers a quick preview of calculated statistics on a selected Input, which will be outputted as a channel, based on selected options under Output channels and Calculation type.

The picture below shows how it looks on the display screen. Channels can be displayed in a variety of graphical widgets, from simple numerical displays to strip charts, bar graphs, and more.

Dewesoft X display showing real waveform (top) and statistical values in the chart below and in the digital metersDewesoft X display screen showing real waveform (top) and statistical values in the chart below and in the digital meters

Learn more about Dewesoft and Statistical Calculations:

Dewesoft PRO Training > Statistical Calculations on Sampled Data

What Is Common-Mode Voltage? What is Common Mode Rejection?

Common mode voltages are signals that are present on both leads of a signal source. In reality, there should not be identical signals on both leads, so common mode is usually noise that has crept into the signal chain.

The best way to eliminate or reduce common-mode voltages is to make a differential measurement. 

To explain, let’s step back a little. In the single-ended measurements mentioned above, we are using one preamplifier to measure the positive signal line. If the noise gets into the signal, how can we tell? How can we know what is the real signal and what is the noise? 

Perhaps from experience, we can see 60 Hz riding on top of the signal, but it’s a challenge.

Representation of a Differential Amplifier
Representation of a Differential Amplifier

The most basic approach to eliminating common-mode signals is to use a differential amplifier. This amplifier has two inputs: a positive one and a negative one. The amplifier measures only the difference between the two inputs.

Common Mode Rejection

Electrical noise riding along on our sensor cable should be present on both lines - the signal positive line and the ground (or signal negative) line. Signals common to both lines will be rejected by the differential amplifier, and only the signal will be passed through, as shown in the graphic below:

A differential amplifier successfully eliminates common-mode voltages within its CMV voltage range
A differential amplifier successfully eliminates common-mode voltages within its CMV voltage range

This works great, but there are limits to how much common-mode voltage (CMV) the amplifier can reject. When the CMV present on the signal lines exceeds the differential amplifier’s maximum CMV input range, it will “clip.” The result is a distorted, unusable output signal, as shown below:

A differential amplifier distorts or clips when its CMV input range is exceeded
A differential amplifier distorts or “clips” when its CMV input range is exceeded

So in these cases, we need an additional layer of protection against CMV and electrical noise in general (as well as ground looping, which will be discussed in the next section) - isolation.

An isolated amplifier’s inputs “float” above the common-mode voltage. They are designed with an isolation barrier with a breakdown voltage of 1000 volts or more. This allows it to reject very high CMV noise and eliminate ground loops.

An isolated differential amplifier rejects even very high CMV
An isolated differential amplifier rejects even very high CMV

Isolated amplifiers create this isolation barrier by using tiny transformers to decouple (“float”) the input from the output, or by small optocouplers, or by capacitive coupling. The last two methods typically provide the best bandwidth performance.

What Is a Ground Loop?

Unless they are prevented, ground loops can be a serious problem for measuring systems. Sometimes called “noise”, a ground loop is caused by inadvertently referencing electrical equipment to more than one path to the ground - any difference of potential at these grounding points causes current to flow between them, inducing a current loop. This causes distortions in the signal which, if high enough, can ruin the measurement. 

In the picture below, the measurement amplifier is connected to the ground (GND 1) on one side. An asymmetrical shielded cable is used to connect the sensor, whose metallic housing is placed on a conductive surface at GND 2. Due to the length of the cable, there is a difference in potential between GND1 and GND 2. This potential difference acts like a voltage source, coupling with the electromagnetic noise from the environment.

A ground loop caused by ground potential differences
A ground loop caused by ground potential differences

If the sensor could be decoupled from GND2, it might solve the problem. But sometimes this is not possible. Furthermore, sometimes the referencing of a cable shield is required by safety rules, and therefore should not be removed.

The best solution is to use a differential amplifier within the signal conditioner which is isolated. With this one change, the problem is solved.

Eliminating differential ground potential problems via isolation
Eliminating differential ground potential problems via isolation

Ground loops can also come from the instrument itself, via its own power supply. Keeping in mind that our measuring system is plugged into power, which has a ground reference. It is critical therefore to decouple this reference from the signal handling components of the instrument to ensure that ground loops cannot be created within the instrument.

Power supply induced ground looping
Power supply induced ground looping

This scenario can become dangerous if there is a wiring fault. Looking at the high current path from the power supply, what will happen if the return line is broken? All of the energy will be routed through the signal conditioning part of the DAQ hardware. This could result in the entire system being damaged or destroyed, and even dangerous potentials for the human operator of the instrument.

The danger of power supply induced ground loops
The danger of power supply induced ground loops

By isolating the signal path completely from the power supply, it is not possible for the scenario above to occur.

Important Isolation Terms

Given all of the information above, it seems clear that our measuring systems should have at least differential and preferably isolated analog signal inputs

But when you’re reviewing the isolation specifications of various measurement systems and signal conditioners, you may find it specified with terms like: 

  • channel-to-ground,
  • channel-to-channel and
  • bank isolated

What do these terms mean, and how do they relate to each other?

Channel-to-Ground Isolation

Channel-to-ground isolation defines the maximum voltage there can be between a channel’s input and instrument ground. Normally an instrument’s ground is referenced to the ground of the power supply. By isolating signal ground from chassis ground we can eliminate most ground loop problems. 

Channel to ground isolationChannel to ground isolation scheme

Sometimes this is also referred to as input-to-output isolation. All of the channels share a common ground, which is isolated from the ground or earth potential of the instrument. This would not be a limitation if only one signal source were connected to the system. But when additional signals are connected, each with ground potential differences, it can lead to noise across all signals and common mode problems. 

If two or more channels share a common ground, then they are not galvanically isolated. Take care when an instrument mentions only input-to-output or channel-to-ground isolation. 

Channel-to-Channel Isolation

Channel-to-channel isolation defines the maximum voltage there can be between a channel and any other channel. Channels cannot share a ground bus, for example. Each channel must also be isolated from the rest of the system, e.g. the system’s power supply voltage, chassis ground, and so on. If all channels are isolated from each other, then they are necessarily also isolated from ground, so channel-to-ground isolation is included within channel-to-channel isolation.

Channel to channel isolation diagramChannel to channel isolation diagram

So, if a system has channel-to-ground isolation, it does not necessarily mean that it has channel-to-channel isolation. BUT, if a system has channel-to-channel isolation, then it must also have channel-to-ground isolation.

SIRIUS DAQ systems from Dewesoft provide both channel-to-channel and channel-to-ground isolation, as shown in this short video:

Bank Isolation

Bank isolation is typically employed by high-channel-count systems. In this scenario, channels are isolated in groups that share common isolation. This can be done either to save money or out of necessity. 

Isolation components take up space and consume power. In very high density measuring systems sometimes there is literally not enough room for each channel to be separately isolated.

When you look at the Dewesoft compatible signal conditioners for voltage later in this article, you will see that the SIRIUS HD (High Density) signal conditioners are bank isolated in pairs, where every two channels share an isolation path. All other SIRIUS signal conditioners are isolated per channel.

See the SIRIUS signal conditioners for voltage measurements in this article.

What are “CAT” Safety Standards?

Looking at instrumentation specifications for high voltage inputs, you will notice terms like “CAT II” and “CAT III”, with some voltage levels next to them. What do these mean?

“CAT” refers to the IEC (International Electrotechnical Commission) measurement category of how and where instruments are used with respect to live circuits. There are four categories, listed by the Roman numerals I, II, III, and IV. 

These CAT values essentially refer to the location of the instrument. The lowest value of this means that the instrument will be located farthest from the high voltage and transient potentials, while CAT IV refers to locations very close to the source of high voltages and therefore transients.

Then within each of these CAT values, you will often see voltage values that refer to the instrument’s ability to withstand transients up to that value. An instrument-rated to CAT II-1000V is of course able to withstand many higher-level transients than an instrument-rated to CAT II-600V.

CAT Value Example Locations

CAT safety standards
CAT Levels and safety standards by location

Basically, the closer the equipment is connected to the primary source of voltage power, the higher the possibility of dangerous transient voltages getting into the instrument, and therefore the higher the CAT number is.

Transient Overvoltage Protection By Working Voltage and CAT

Category Working Voltage Peak Transient Test Source
CAT II 600 V 4000 V 12 Ω
CAT II 1000 V 6000 V 12 Ω
CAT III 600 V 6000 V 2 Ω
CAT III 1000 V 8000 V 2 Ω
CAT IV 600 V 8000 V 2 Ω

In the table above, “working voltage” refers to DC or ACRMS to ground. The peak transient refers to 20 impulses at the given voltage level. The test source impedance comes from V/A.

Notice also that the source impedance for CAT III and above is 2 Ω versus 12 Ω for CAT II! 

According to A = V/R (Ohm’s law - a basic tenet of electrical engineering), a 2 Ω source has six times the current flowing than a 12 Ω source. This is why the CAT number itself is more important than the voltage value that follows it. For example, a CAT II-1000V rated instrument is not superior to one rated to CAT III-600V because of this source impedance difference.

So how do you know what CAT level and voltage to require for your high voltage application? Because high voltages involve not just the safety of your equipment but the safety of human operators, always consider the worst-case in terms of dangerous high voltage transients and choose an instrument that will protect you and your colleagues.

Dewesoft Signal Conditioners With CAT Ratings

Product Range Signal Conditioner CAT Level CAT Voltage
  1xHV CAT III 600 V
  1xTH-HV CAT II 1000 V
  1xTH-HV CAT III 600 V

What is Signal Overload / Overmodulation?

When signal levels are higher than expected, they are clipped by the ADC converter, resulting in wrong measurements, which means you have to do the test all over again. This is called signal overload, clipping, and overmodulation, among other terms.

Engineers have been struggling with high dynamic range signals for decades. Dynamic range refers to the difference between the smallest and largest amplitude excursions of a signal. Imagine that you are making a measurement and most of the time the signal is in the millivolt range, but occasionally it jumps up to 80 V. If you set the input range to 100V in order to avoid clipping when the signal rises, the resolution of the signal when it’s in the millivolt range will not be optimal.

Engineers have addressed this by inputting the same signal into two channels of their measuring system and setting the gains differently. This more or less solves the problem but it creates two more problems: 

  1. You need twice as many measurement channels in your system.
  2. Analyzing the data is far more difficult because you have to manually combine the data sets from the two channels after the test to create a composite set of data for each channel. This is an enormous workload and additional analysis burden, especially when multiplied by many channels.

A better solution would be a DAQ system where each input channel really had two ADCs inside, each set to a different gain, and a fast processor that would automatically choose the one that best represented the signal and combine them into a single data stream. 

Does that sound too good to be true? It has already been done by Dewesoft with their SIRIUS DualCore® ADC technology. Each channel amplifier has two ADC’s that always measure the high and low gain of the input signal. This results in the full possible measuring range of the sensor and prevents the signal from being clipped.

Above is a video that shows and explains more about how it works.

Dewesoft’s DualCoreADC® technology achieves more than 130 dB signal to noise ratio and more than 160 dB in dynamic range. This is 20 times better than 24-bit systems and 20 times less noise.

Voltage Transducers

Every instrument that can measure an analog voltage signal can do so directly, right? So why would we ever need a voltage transducer?

Nearly every DAQ system and data logger in the world can directly accept low and medium voltages in the ranges of 0-10V or 0-50V, so we do not need a sensor or transducer to reduce or convert this voltage in any way. From 50V to approximately 1000V there are signal conditioners available for DAQ systems such as the Dewesoft SIRIUS HV module, which can directly and safely accept these voltages and internally step them down so that they can be digitized, displayed and stored.

But at higher voltages, or in any case, when life-threatening currents and voltages are present, it is essential to use a high voltage transformer to step down the high voltage and isolate the human test operator from dangerous voltage and current. Such a device is called either a Voltage Transformer (VT) or a Potential Transformer (PT).

Typical Potential TransformerTypical Potential Transformer

The typical PT sensor includes a transformer to step down a very high potential - even higher than 10kV - down to a safe level. It can be placed in series with or across the circuit being monitored. The transformer’s primary winding has a large number of turns compared to the secondary. 

Because the data acquisition device connected typically has a very high impedance, very little current will flow, therefore the PT’s secondary winding experiences almost no load at all. Most PTs output between 50 and 200V, which nearly every DAQ system can accept.

PTs are available for outdoor usage and those designed for indoor usage. There are also those designed for electrical metering applications. There is also an alternative to the pure transformer type which uses a bank of capacitors after an intermediate transformer to further step down the voltage. These can be less costly because the relatively low step-down ratio intermediate transformer is less expensive than the conventional wound transformer with a high step-down ratio. 

A third variant is the optical VT. Optical VTs are usually found in power substations, and not often in DAQ applications. Since they operate on the principle of the Faraday effect, whereby the polarization of light is affected directly by a magnetic field, they are inherently isolated. They are also extremely accurate.

Outdoor 36 and 200 kV outdoor VTsOutdoor 36 and 200 kV outdoor VTs. Photo courtesy of ABB.

Voltage Transducer Applications

  • Energy Production and Distribution high voltage power line testing, synchronizing generators with the main power grid, 
  • Aerospace - engine and power system testing
  • Automotive - electrical circuit system test, hybrid, and electric motor tests
  • Transportation - electric subway cars, third rail and pantograph tests, electrical energy distribution centers

Voltage Transducer Pros

  • They provide essential safety to the test engineer and technician
  • Easy to use
  • Most models do not require external power
  • Long-life operation

Voltage Transducer Cons

  • Can be expensive

What is Aliasing?

Let’s say your AC voltage is a 10 kHz sine wave, but you only take one sample from it every second. Obviously, the resulting recording is going to be completely wrong. 

Between each sample that you take, 10,000 sine waves will have gone by. The resulting “signal” will look like a waveshape, but it will be completely wrong. It will be an “alias” of the actual signal. It is dangerous because you get something that looks like a signal, but of course, it’s wrong.

Let’s use a practical example. The graphic below represents the real signal that we are trying to measure:

Analog signalThe signal that we want to measure

Now imagine that we are not sampling it fast enough. In fact, we are sampling at the rate shown by the dots in the graph below:

Actual sample locations shown in redActual sample locations are shown in red

You can probably already see what our “signal” is going to look like after this process:

Aliased signalAliased signal 

This is a completely wrong result: it does not resemble the actual signal at all. Let’s compare them side by side:

Analog signalAliased signal

Left: Actual signal
Right: Aliased signal

The most obvious solution to aliasing is to simply sample faster, to ensure that the frequencies of your signals will never be higher than the sample rate can handle.

But in a practical sense, this is not always possible. Sometimes unexpected transients happen, for example. 

If we filter in the analog domain before the ADC, we can prevent the aliasing problem from ever occurring. Note that it is still important to set a high enough sample rate to capture the frequency range of interest, but at least with Anti-Aliasing Filters (AAF), we will avoid false (“alias”) signals from destroying the integrity of our measurements. 

The ideal AAF would have a very flat passband AND very sharp cutoff at the Nyquist frequency (essentially half of the sample rate). 

Anti-aliasing filter roll-off diagramAnti-aliasing filter roll-off diagram

Typical AAF configuration: a steep low-pass analog filter before the ADC prevents signals more than half of the maximum bandwidth of the ADC from passing. This is what Dewesoft does with its 16-bit SAR ADCs as found in SIRIUS-HS modules.

However, with their 24-bit Delta-sigma ADCs, as found in SIRIUS, KRYPTON, and IOLITE data acquisition system nearly the entire product line, Dewesoft DAQ systems have an additional DSP filter on the ADC itself that automatically adjusts based on the sample rate that the user has selected. This multi-stage approach provides the most robust anti-aliasing filtering available in DAQ systems today. 

Dewesoft’s fast sigma-delta ADC technology is the best possible approach to preventing aliasing.

Devices For Common Voltage Measurement

Voltage is one of the most often recorded signals, and virtually every DAQ hardware in the world can measure it to one degree or another. Other instruments can also measure voltage, such as laboratory oscilloscopes and voltmeters, just to name a few.

Voltmeters are very accurate but have low bandwidth, while oscilloscopes have very high bandwidth but are not as accurate, for example. The table below breaks them down by low and high ranges, accuracy and bandwidth:

Instrument Low V Range High V Range Accuracy Bandwidth
Voltmeter /
Digital Multimeter
Millivolts 1000 V Very Good Very low
Oscilloscope Millivolts 50 V (higher with a divider) Fair to Good Very high
Data Logger Low volts 100 V Fair to Good Low
DAQ System Microvolts or Millivolts 100 V to 1000 V Very Good Medium
Power Analyzer Millivolts 100 V to 1000 V Very Good Medium

The numbers are just generalizations: there are many instruments on the market, and their specifications can vary greatly.

In addition, you sometimes need to measure very tiny voltages, i.e., in the microvolt range ... and all the way into the thousands of volts. A voltage preamplifier with multiple input ranges is needed to convert these widely different signal levels to a normalized output which can be digitized. Sometimes a tiny voltage is riding on top of a large DC offset, which is yet another challenge that many measuring systems have trouble with.

Compatible Dewesoft Devices for Voltage Measurement by Voltage Range

  0-10 V 0-50 V 0-200 V 0-1000 V 1000 V+
  √ compatible (xxx) = requires modules and/or accessories
SIRIUS √ (LV, HV, STG, ACC) √ (LV, HV) √ (HV) √ (HV) √ (PT)
√ (LV, STG) √ (LV) √ (STG + DSI-V-200) √ (LV + PT) √ (LV + PT)
(single channel)
√ (LV, HV, ACC, STG) √ (LV, HV, STG) √ (LV, HV, STG + DSI-V-200) √ (HV) √ (HV + PT)
IOLITE √ (LV, STG) √ (LV, STG) √ (STG + DSI-V-200) √ (STG + PT) √ (STG + PT)
IOLITEd √ (LV, STG) √ (LV, STG) √ (STG + DSI-V-200) √ (STG + PT) √ (STG + PT)
DEWE-43A √ (DSI-V-200) √ (DSI-V-200) √ (PT) √ (PT)
MINITAURs √ (DSI-V-200) √ (DSI-V-200) √ (PT) √ (PT)

PT = Potentiometric Transformer is absolutely required for safety, isolation, and voltage division

SIRIUS Data Acquisition Systems

SIRIUS HS (High Speed) DAQ systems are available in a wide range of physical configurations, from modular “slices” that connect to your computer via USB or EtherCAT, R3 rack-mounting systems, and R1, R2, and R8 stand-alone systems that include a built-in computer.

SIRIUS DAQ system different chassis optionsThe SIRIUS data acquisition system product line-up

If you take a look at Dewesoft’s SIRIUS DualCore and SIRIUS HS signal conditioners, you will see that all of these modules provide channel-to-channel and channel-to-ground isolation voltage of 1000V (the HV module is additionally CATII safety-rated). SIRIUS HD high-density amplifiers are isolated ±500V in pairs. 

In the real world of data acquisition, there are often more than just the signal inputs - signal conditioners often provide excitation voltage or current to power the sensors. Strain gages, load cells, RTDs, LVDTs and IEPE accelerometers are all good examples of sensors that require power.

Sometimes overlooked by DAQ system makers, it is important that these excitation lines be isolated, which is why Dewesoft provides isolation and/or differential inputs and over-voltage protection with direct short-to-ground capability across its product line, and protects its instruments and human operators from ground loops.

SIRIUS DualCore® Modules for Voltage

High dynamic range SIRIUS modules and their compatibility with voltage measurements directly, and using DSI adapters:

  SIRIUS DualCore® modules(up to 8 input channels per SIRIUS slice)
Low voltage
High voltage
Input Ranges ±200V, ±20V, ±10V, ±1V, ±100 mV ±1200 V, ±50 V ±50V, ±10V, ±1V, ±100mV ±10V, ±1V, ±100 mV, ±10 mV ±10 V, ±500 mV
Input Coupling DC, AC 1Hz (3, 10 Hz SW) DC DC, AC 1Hz (3, 10 Hz SW) DC DC, AC 0.1Hz, 1Hz
Sensor Excitation 2..30 V bipolar, 0..24 V unipolar, max. 0.2A/2W N/A 0..20 V max. 0.8W, 0..60mA max 0.5W 0..15V max. 44mA (IEPE only) 2,4,8,12,
Isolation Voltage 1000 V CATII 1000V 1000 V 1000 V 1000 V

Note: Sensor excitation in the LV module requires the DB9 input connector.

SIRIUS HD - High-Density Modules for Voltage

High-density SIRIUS module with up to 16 channels per SIRIUS slice for high channel count applications.

  SIRIUS HD (High Density) modules (up to 16 input channels per SIRIUS slice)
Low voltage


Input Ranges ±100V, ±10V, ±1V, ±100 mV ±10V, ±1V, ±100 mV, ±10 mV ±10 V, ±5V, ±1V, ±200mV
Input Coupling DC DC DC, AC 0.1 Hz, 1Hz
Sensor Excitation 2..30 V bipolar, 0..24 unipolar, max. 0.2A/2W 0..12V max. 44mA IEPE only
4,8,12 mA
Isolation Voltage 500 V in pairs 500 V in pairs 500 V in pairs

Note: Sensor excitation in the LV module requires the DB9 input connector.

SIRIUS HS - High-Speed Modules for Voltage

1 MHz 16 bit SAR technology with software selectable alias-free filtering is the perfect choice for transient recording. Up to 8 channels per SIRIUS module.

  SIRIUS HS (High Speed) modules (up to 8 input channels per SIRIUS slice)
Low voltage
High voltage
Input Ranges ±100V ... ±50 mV ±1600 V ... ±20 V ±50V ... ±20 mV ±10V ... ±100 mV
Input Coupling DC, AC 1Hz (3, 10 Hz SW) DC DC, AC 1Hz (3, 10 Hz SW) DC, AC 1Hz (3, 10 Hz SW)
Sensor Excitation 2..30 V bipolar, 0..24 V unipolar, max. 0.2A/2W N/A 0..20 V max. 0.8W, 0..60mA max 0.5W IEPE only
4,8,12 mA
Isolation Voltage 1000 V CATII 1000V 1000 V 1000 V

Note: Sensor excitation in the LV module requires the DB9 input connector.

Learn more about SIRIUS DAQ systems.

Learn more about SIRIUS technical specifications.

DEWE-43A and MINITAURs DAQ systems

The DEWE-43A is an extremely portable, handheld general-purpose data acquisition system. Connecting to your computer via a locking USB connector, it features eight universal analog inputs which can measure low voltages directly, and voltages up to ±200V using DSI-V-200 adapters.

The analog inputs are differential but not isolated It’s “big brother” is called the MINITAURs - this is essentially the DEWE-43A combined with a computer and a few other features, in a single highly portable enclosure. The universal inputs of both systems are compatible with Dewesoft’s DSI adapters, allowing you to connect an RTD sensor to any or all of their eight input channels. 

DEWE-43A and MINITAURs data acquisition systems from DewesoftLeft: DEWE-43A handheld DAQ system
Right: MINITAURs model, including built-in computer

Both models have differential universal inputs, which are basically full-bridge / low voltage modules that are compatible with DSI series adapters, which are available for many different sensors as well as voltages up to ±200V as mentioned above. DSI adapters use TEDS technology to automatically configure themselves in Dewesoft X DAQ software. Simply plug the DSI adapter into the selected input’s DB9 input, verify your settings on the hardware setup screen in Dewesoft X software, and you’re ready to start making measurements.

DEWE-43A and MINITAURs for Voltage Measurement

Voltage Ranges (direct) ±10 V, ±1 V, ±100 mV, ±10 mV DualCoreADC high and low ranges:
±10V (500 mV), ±1V (50 mV), ±100mV (5 mV), ±10mV (0.5 mV)
Voltage Ranges using DSI-V-200 Up to ±200 V Up to ±200 V
Input Coupling DC DC
Sensor Power ±5 V ±0.1 % bridge sensor supply, 70 mA limit (not available when DSI adapter is used) 0 to 12 VDC software programmable (16-bit DAC), max 44 mA (not available when DSI adapter is used)
Input Type Differential Differential
Overvoltage Input Protection +70 V In+ to In-: 50V continuous; 200 V peak (10 ms)

Learn more about DEWE-43A.

Learn more about MINITAURs.

Learn more about DSI adapters.

KRYPTON and KRYPTON ONE Data Acquisition Systems

KRYPTON is the most ruggedized range of products available from Dewesoft. Built to withstand extreme temperature and shock and vibration conditions, KRYPTON is rated to IP67, protecting them against water, dust, and more. They connect to any Windows computer (including Dewesoft’s own ruggedized IP67 KRYPTON-CPU model) via EtherCAT and can be separated by up to 100  meters (328 feet), allowing you to locate them near the signal source. Like SIRIUS, they run the most powerful DAQ software on the market, Dewesoft X. 

KRYPTON DAQ system with Dewesoft DSI adaptersA typical multi-channel KRYPTON module with various DSI adapters connected

These extremely rugged systems are also available in single-channel modules called KRYPTON-1. Both the multi-channel and single-channel KRYPTON provide the same level of performance and environmental robustness.

KRYPTON multi-channel modules for Voltage

KRYPTON multi-channel modules  
High Isolation Voltage
Number of Channels 4 or 8 channels 3 or 6 channels 4 channels
Voltage Range ±50 V ±10V, ±1V, ±100mV, ±10mV ±10 V, ±5 V, ±1 V, ±200 mV
Input Coupling DC DC DC, AC 0.1 Hz, 1 Hz
Sensor Excitation N/A 0...15 V max. 0.4W/ch 
(45mA limit)
IEPE 4 mA, 8 mA
Isolation Voltage 1000 V Differential Differential

KRYPTON ONE Single-channel Modules for Voltage

KRYPTON-1 single-channel modules
Voltage Ranges ±50 V, ±10 V, 
±1 V, ±100 mV
±1000 V ±50 V, ±10 V, 
±1 V, ±100 mV
±10 V, ±5 V, ±1 V, ±200 mV
Input Coupling DC, AC 1Hz DC DC, AC 1Hz DC, AC 0.1 Hz, 1 Hz
Sensor Excitation N/A DC Freely programmable
via 16-bit DAC)
IEPE only
4 mA, 8 mA @ 24 VDC
Isolation Voltage 125 VRMS
CAT II 1000 V
125 VRMS
125 VRMS


Above left: KRYPTON ONE HV module
Above left: KRYPTON ONE HV module

Learn more about KRYPTON DAQ instruments.


IOLITE is a unique product that combines the essential capabilities of a real-time industrial control system with a powerful DAQ system. With IOLITE, hundreds of analog and digital channels can be recorded at full speed while simultaneously sending real-time data to any third party EtherCAT master controller.

IOLITE data acquisition systemLeft: IOLITEr rack-mounting system with 12 input module slots
Right: IOLITEs bench-top system with 8 input module slots

IOLITE multi-channel input modules
Low Voltage
Number of Channels 8 6
Voltage Ranges ±100 V, ±10 V
(±10 V, ±1V on request)
±50 V, ±10 V, ±1 V, ±100 mV
Input coupling DC DC, AC 1 Hz
Sensor Excitation N/A 0 - 12 V (bipolar), 0..24 V (unipolar) max. 0.4 W/ch
Isolation Voltage 1000 V Differential

Learn more about IOLITE DAQ and Control systems.