The LabJack T7 is the most versatile, best bang-for-your-buck DAQ offered by LabJack or anyone else that we know of. Of course, it isn't perfect for every application or project. Compare all LabJack hardware side by side or read a detailed comparison of the different LabJack devices.

DAQ stands for data acquisition. It is the process of collecting analog data like temperature and pressure from sensors, instruments and other devices and turning it into digital formats. This digitized data is then stored in a computer for faster analysis and reporting. 

A DAQ system allows real-time monitoring, data logging and analysis.  It is used in various fields such as scientific research, industrial automation, quality control and more. Combined with customized software and scripts- a DAQ system can be used as a powerful tool to improve and refine new designs ore test and automate with speed and precision. 

LabJack offers computer-based DAQ solutions. This means the LabJack is designed and most powerful when connected to a computer via USB, Ethernet or WiFi to configure, run software, and record measurements. 

Watch this video for a quick look at how it works.

The DAQ system has four major components:

1. a DAQ device (the LabJack)that acts as the interface between your

2. computer and 3. external sensors or devices, and

4. DAQ software that can store, analyze and report the data.

To choose a DAQ device that meets your specific performance specifications, determine your needs in terms of speed for capturing data or the level of detail in the measurements. Consider your voltage range and channel count, along with how many devices or sensors you need to connect one time.

For example, the LabJack T4 is best for engineering students or hobbyists who need an affordable and easy-to-use DAQ device for simple tests. The LabJack T7, typically used in laboratory or industrial settings, has higher analog input resolution (16 bit) for more precise measurements, and internal amplification for tiny signals like Thermocouples, Bridge Circuits and Load Cells. 

LabJack offers more than just the little red box that includes hardware, detailed datasheets, app notes, software and legendary customer support. Our engineers can recommend the right DAQ system for your application and goals.

To speak with our engineers, click the chat bar at the bottom right of any page, or see our Contact page for other ways to get in touch with us.

What is resolution?

Resolution in this context refers to the conversion of an analog voltage to a digital value in a computer (and vice versa). A computer is a digital machine and thus stores a number as a series of ones and zeroes. If you are storing a digital 2-bit number you can store 4 different values: 00, 01, 10, or 11. Now, say you have a device which converts an analog voltage between 0 and 10 volts into a 2-bit digital value for storage in a computer. This device will give digital values as follows:

So in this example, the 2-bit digital value can represent 4 different numbers, and the voltage input range of 0 to 10 volts is divided into 4 pieces giving a voltage resolution of 2.5 volts per bit. A 3-bit digital value can represent 8 (2³) different numbers. A 12-bit digital value can represent 4096 (2¹²) different numbers. A 16-bit digital value can represent 65536 (2¹⁶) different numbers. It might occur to you at this point that a digital input could be thought of as a 1-bit analog to digital converter. Low voltages give a 0 and high voltages give a 1.

In the case of the LabJack U12, a single-ended analog input has a voltage range of -10 volts to +10 volts (20 volt total span) and returns a 12-bit value. This gives a voltage resolution of 20/4096 or 0.00488 volts per bit (4.88 mV/bit).

Single-ended and differential refer to the reference for a voltage. Single-ended is referred to ground while differential is referred to some other voltage. For a single-ended measurement, the LabJack converts the difference between the voltage at an input and ground. For a differential measurement, the LabJack converts the difference between the voltage at one input and the voltage at another input that is not necessarily ground.

Differential does not refer to whether a signal is positive & negative or positive-only.  The terms for that are bipolar and unipolar.

On the LabJack U3, U12, U6, and T7, analog inputs can set as single-ended or differential via software. Analog inputs on the LabJack UE9 are single-ended only, so an instrumentation amp is needed to convert a differential signal to single-ended, or a pseudo-differential measurement can be made by taking the difference of two single-ended measurements.

Also see the Differential Readings App Note.

DIO = Digital Input/Output
IO/D/FIO/EIO/CIO/MIO = Somewhat arbitrary monikers for specific DIO ports on different LabJacks. 

Digital I/O stands for Digital Input and Output. Digital Inputs allow a microcontroller to detect logic states, and Digital Outputs allow a microcontroller to output logic states.

Each digital I/O on a LabJack can be individually configured to one of 3 states: input, output-high, or output-low.

Digital Input: A digital input detects if a voltage is above/below a specific threshold. If the voltage is higher than some value, the computer will detect the digital input as high/set/1. If the voltage is lower than some value, the computer will detect the digital input as low/clear/0.

Digital Output: A digital output allows you to control a voltage with a computer. If the computer instructs the output to be high, the output will produce a voltage (generally about 5 or 3.3 volts). If the computer instructs the output to be low, it is connected to ground and produces no voltage.

Example:

Turn an LED On/Off using a digital I/O.

1. Wire the LED as shown. Optionally connect a current-limiting resistor.
2. Set the state of FIO0 to output-high on the computer. The LED will turn on.
3. The LED will turn Off if the state of FIO0 is set to output-low.

If you are using a raw bridge sensor/load cell/strain gauge that is ratiometric (mV/V) and are simply looking for guidance on which products to use, we suggest using a LabJack T7 and LJTick-VRef41 for the best measurements and ease of use.

For a detailed guide read the LabJack Bridge Circuit App Note

The Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities.

Keywords: loadcell, strain gauge, strain gage, bridge circuits, potentiometer, raw bridge circuit, H-bridge, iepe, Integrated Electronics Piezo-Electric

U3 compared to U12

The U3 is newer than the U12, and in general is faster, more flexible, and less expensive.

The U3 is about half the size of the U12. The enclosure can be mounted using a couple screws or DIN rail, whereas the U12 enclosure has no mounting options.

Command/response functions on the U3 are typically 5-20 times faster than on the U12. See Section 3.1 of the U3 User's Guide compared to the U12 data rates page.

The U3 has up to 16 analog inputs compared to 8 on the U12. Any channel can be measured differentially versus any other channel. Accuracy specs are better than the U12.

The U3-LV has single-ended ranges of 0-2.4 or 0-3.6 volts, and a differential range of ±2.4 volts (pseudobipolar only). The U3-HV has 12 flexible I/O capable of those same low-voltage ranges, and 4 high-voltage analog inputs with a range of ±10 volts or -10/+20 volts. The U12 has a ±10 volt single-ended input range, and differential input ranges varying from ±20 volts to ±1 volt (all true bipolar). The circuitry used by the U12 to provide those high bipolar ranges is simple and inexpensive, but has drawbacks including relativity poor input impedance and errors which are different on every channel. There are many devices on the market now that have copied the same circuitry from the U12 and have the same drawbacks.

The U3 supports input streaming with a max rate of up to 50 ksamples/second, compared to 1.2 ksamples/second for the U12. The U3 achieves the full 12-bit resolution up to 2.5 ksamples/second, and then as speed increases the effective resolution drops to about 10 bits due to noise.

The U3 has 2 10-bit DACs as does the U12. The DACs on the U3 are derived from a regulated voltage, whereas the U12 DACs are derived from the power supply, so the U3 DACs will be more stable.

The digital I/O on the U3 use 3.3 volt logic, and are 5 volt tolerant. The U12 has 5 volt logic.

The U3 can have up to 2 timers and 2 counters. The timers have various functionality including period timing, duty cycle timing, quadrature input, pulse counting, or PWM output. The U12 has 1 counter and no timers.

The U3 has master support for SPI, I2C, and asynchronous serial protocols. The U12 does not support I2C, but does have some SPI and asynchronous support.

The U3 is supported on Windows, Linux and Mac OS X. The U12 has full support for Windows, limited support for Linux, and limited public support for the Mac.

On Windows, the U3 uses the flexible UD driver which also works with the U6 & UE9. There is a specific separate driver for the U12.

The U3 is compatible with the LJTick signal conditioning modules, whereas the U12 is not. Current ticks include:

• LJTick-Divider (LJTD): Divides 2 single-ended higher voltage analog signals down to 0-2.5 volt signals. Install different resistors for different gain and offset.
• LJTick-DAC (LJTDAC): Provides a pair of 14-bit analog outputs with a range of ±10 volts.  Plugs into any digital I/O block, and thus up to 10 of these can be used per U3/UE9 to add 20 analog outputs.
• LJTick-InAmp (LJTIA): Provides two instrumentation amplifiers ideal for low-level signals such as bridge circuits (e.g. strain gauges) and thermocouples. Each amplifier converts a differential input to single-ended.
• LJTick-RelayDriver (LJTRD): Allows 2 digital I/O lines on a U3/UE9 to each control a relay or other moderate load up to 50V/200mA.
• LJTick-CurrentShunt (LJTCS): Converts a 4-20 mA current loop input signal into a 0.47-2.36 volt signal.
• LJTick-Proto (LJTP): Consists of an 8x8 grid of holes for prototyping custom signal-conditioning ticks.

... versus UE9: (EOL)

The UE9 has all the same improvements as the U3 above, with the following additions and differences:

The UE9 is about twice the size of the U3.

The biggest difference is that the UE9 supports Ethernet communication in addition to USB. Ethernet communication uses standard TCP or UDP protocol, and supports Modbus/TCP. Ethernet speeds in command/response or stream mode are generally similar to USB speeds (see Sections 3.1 and 3.2 of the User's Guide for more information). The addition of an 802.11 WiFi bridge allows for inexpensive wireless data acquisition and control.

When using Ethernet only (not USB), the UE9 has at least 500 volts of electrical isolation.

The UE9 has 14 analog inputs and 2 analog outputs. The analog inputs and outputs on the UE9 have better accuracy, resolution, and linearity. The analog inputs are single-ended only, but the LJTick-InAmp can be used for low-level differential signals.

Each analog input can be configured individually as unipolar (four ranges from 0-5 volts to 0-0.625 volts) or true bipolar (±5 volts). Analog input resolution is 12-bits at max speed (12 us conversion time), increasing up to 16-bits at slower speeds (2.7 ms conversion time).

Maximum input stream rates range from 250 samples/second at 16-bit resolution to 50+ ksamples/second at 12-bit resolution. The UE9 has a very large 4 Mbit buffer for stream data, compared to a very small buffer on the U3.

The UE9 has up to 6 timers available compared to 2 on the U3.

The UE9-Pro has all the features of the normal UE9 with the addition of an auxiliary low-speed hi-resolution (24-bit) sigma-delta ADC. This converter takes about 125 ms per sample and provides an effective resolution of about 20-bits (18-bits noise free) over the 0-5 or ±5 volt ranges. Linearity and accuracy are also improved compared to the normal converter (which is still available on the UE9-Pro).

... versus U6:

The U6 is similar to a UE9 without Ethernet, but the U6 is newer and has some analog input improvements.  Some key details:

USB only.

Up to 4 timers available.

20 digital I/O (compared to 23 on the UE9).

The U6/U6-Pro analog inputs have higher resolution than the UE9/UE9-Pro in most cases.

Analog inputs are single-ended or differential, with input ranges of ±10, ±1, and ±0.1 volts.

2 Fixed Current Outputs (200/10 μA).

... versus T7:

The T7 is similar to a U6 and UE9, but the T7 combines the benefits of both devices, namely the high quality analog of the U6 with the advantages of Ethernet that you get from the UE9. The T7-Pro extends the advantages even further by adding WiFi.

Other improvements over the U6 and UE9 include:

Supported by our 3rd generation cross platform LJM library.

Straightforward low-level interface that uses Modbus TCP registers to access all device functionality.

Compatibility with most SCADA Modbus TCP enabled systems for both wired and wireless operation.

12 digital I/O lines can be configured for various timing/counting functionality, which we now refer to as DIO extended features. Read more in the DIO EF section of the T-series datasheet.

23 digital I/O, up from 20 on the U6.

The analog input extended feature system (AIN-EF) has the ability to do math and processing in hardware.  Calculations for things like average, RMS, and thermocouples can be done on the device.

Write Lua scripts that run on the device with or without a host computer.

Improved slot-style screw mounts on the enclosure, which makes it possible to wall mount the T7 in any orientation, and still have the ability to quickly 'un-hook' it from the screws.

... versus T4:

The T4 is a blend of a U3-HV and T7.  It has the form factor and I/O of the U3-HV, analog specifications very similar to the U3-HV (e.g. 12-bit analog inputs), but it has the processor of the T7 resulting in various changes compared to the U3:

• Like all T-series devices, the T4 has Ethernet in addition to USB.
• Add a standard WiFi bridge for inexpensive wireless data acquisition and control.
• Supported by our 3rd generation cross platform LJM library.
• Straightforward low-level interface that uses Modbus TCP registers to access all device functionality.
• Compatibility with most SCADA Modbus TCP enabled systems for both wired and wireless operation.
• 10 digital I/O lines can be configured for various timing/counting functionality, which we now refer to as DIO extended features. Read more in the DIO EF section of the T-series datasheet.
• The analog input extended feature system (AIN-EF) has the ability to do math and processing in hardware.  Calculations for things like average and RMS can be done on the device.
• Write Lua scripts that run on the device with or without a host computer.
• The T4 has 4 single-ended analog inputs with +/-10V range, plus up to 8 digital I/O lines can be configured as single-ended analog inputs with 0-2.5V range.  Similar but not exactly the same as the U3 AIN system.

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AIN (Analog Inputs)

A1. My analog input is stuck on some wrong value.

• See Suspicious Values.

A2. My analog input is returning varying values but not the right value.

• See the Troubleshooting Your Analog Input Signal App Note.

A3. My readings are too noisy.

• See Too Much Noise.

A4. How do I measure temperature using a thermocouple, RTD, thermistor or other?

• Start on the Temperature Sensors App Note.

A5. My thermocouple readings are wrong.

• Determine if the error is from the cold junction sensor, the A/D conversion, or the signal itself.
• If the cold junction reading is off by a few degrees that error will show up in your calculated thermocouple temperature.
• Remove the thermocouple, and instead jumper the analog input (or both analog inputs for differential) to GND. The thermocouple voltage is now 0.0 volts which is saying both ends of the thermocouple are at the same temperature and thus the thermocouple temperature you calculate will be equal to the cold junction temperature.
• Remove the thermocouple from the system under test and instead just set it next to the LabJack so the thermocouple is measuring air temperature near the LabJack. If the terminals you are connecting to are at air temperature (e.g. CB37 terminals), the expected voltage is 0.0 volts. If the terminals you are connecting to are warmer than air temperature (e.g. T7 terminals), the expected voltage is a negative value dependent on the temperature difference.
• See Thermocouple Complications.
• See Thermocouple Troubleshooting Tips.

A6. I need to monitor a 4-20 mA current loop signal or measure some other current.

• LabJack analog inputs measure voltage. The LJTick-CurrentShunt is an easy way to convert 4-20 mA to voltage.  See the Measuring Current App Note.

A7. Should I use differential?

• Sometimes it is required or a good idea. See Why use Differential.

A8. Problem with differential analog inputs.

• The signals cannot be totally floating.  See Differential inputs must have a reference.
• See Differential Test.

A9. How do I read from a load cell?

• Most load cells are raw bridge circuits.  See the Bridge Circuits App Note.

A10. How do I measure pressure?

• See the Pressure Sensors App Note.

A11. Can I measure AC or DC?

• Yes, both. When you ask for 1 sample from the LabJack you get the voltage at that moment.  If the signal is DC, you expect multiple samples over time to return the same value.  If the signal is AC, the samples are taken at different points of the waveform and thus will return different values.
• If you want to acquire the waveform for an AC signal, you simply acquire multiple samples over time, which is often done using stream mode.  Then if wanted you can do math on the waveform to determine parameters such as max/min, RMS, or frequency.
• On T-series devices you can use the AIN-EF system to acquire multiple samples over time, do some math, and return various values that describe the multiple samples (RMS, Peak-to-Peak, Period, Average, Max/Min).
• See the Measuring 120/240 VAC App Note.

A12. What is the max data rate?

• We have lots of detail for sample rates.  U12, U3, U6, UE9, T-Series.
• For stream mode we usually specify the max sample rate. For max scan rate divide the max sample rate by number of channels. SampleRate = ScanRate * NumChannels.
• Extended channels on the Mux80 act just like normal channels.  The max sample rate of the LabJack is still the same, you just use a bigger number for NumChannels in the above equation.

LabJack hardware can be connected to nearly any analog or digital sensor. Of course some sensors are easier than others to connect. If you haven't yet purchased your sensors please check out our App Notes for detailed guides and best practices. Generally the best sensors output an analog voltage in the 0-10v DC range. We have many signal conditioning modules we refer to as "Ticks" that make it easy to accept other signals and ranges

• LJTick-Current Shunt for 4-20mA signals
• LJTick-Divider for voltages over 10v
• LJTick-Vref for sensors that require a stable excitation/power source
• LJTick-Resistance for RTDs, Thermistors or resistive sensors
• LJTikc-InAmp for amplifying tiny signals like bridge circuits or thermocouples

LJM Library

using LabJack;

    ...

    int handle;
    LJM.OpenS("T7", "USB", "ANY", ref handle);

    // Read the voltage on AIN0
    double voltage;
    LJM.eReadName(handle, "AIN0", ref voltage);

    ...

Read the output of sensors which measure voltage, current, power, temperature, humidity, wind speed, force, pressure, strain, acceleration, RPM, light intensity, sound intensity, gas concentration, position, and many more. A LabJack brings this data into a PC where it can be stored and processed as desired.

Control things like motors, lights, solenoids, relays, valves, and more.

Visit our Blog for detailed examples, case studies and customer projects.

AI or AIN = Analog Input
ADC = Analog to Digital Converter

An analog input converts a voltage level into a digital value that can be stored and processed in a computer. Why would you want to measure voltages? There are a multitude of sensors available which convert things like temperature, pressure, etc. into voltages.  The voltages can then be easily measured by various kinds of hardware, such as a LabJack U3-HV, and then read into a computer.  The computer can then convert the voltage value into it's original type (temperature, pressure, etc) and the value can then be stored in a file, emailed to someone, or used to control something else outside of the computer.

Example:

Get temperature from a sensor using an analog input.

1. Wire the output of the analog temperature sensor to a U3-HV as shown.
2. Read the voltage on the computer to know the current temperature. 
3. This particular sensor outputs 0.01 volts per °F, so 0.76V corresponds with 76°F.

Explore LabJack's Analog Input App Note