14.0 Analog Inputs [T-Series Datasheet]

Overview

An analog input (commonly referred to as AIN or AI) uses an analog-to-digital converter (ADC) to convert a voltage difference into a digital value.

LabJack T-series devices feature multiple analog inputs. Each device has a range of features to support diverse measurement needs. The below guides discuss the capabilities of each device:

Common Uses

LabJack’s T-series DAQ devices provide analog inputs which are capable of versatile signal measurement. They work with large signals, small signals and, with some signal conditioning can even measure current signals such a 4-20mA. LabJack publishes many app-notes to help you navigate the wide world of analog signals:

General Analog Input App Notes: Analog Input App Notes.
Sensor-Specific App Notes: Sensors App Notes
Application-Focused App Notes, such as: temperature sensors and thermocouples

AIN Extended Features

T-series AIN Extended Features simplify operations such as:

Reading thermocouples and thermistors
Calculating RMS, RTD, average/max/min, average/threshold, and circuit element resistance

Floating Inputs

The analog inputs are not artificially pulled to 0.0 volts, as that would reduce the input impedance, so readings obtained from floating channels will generally not be 0.0 volts. The readings from floating channels depend on adjacent channels and sample rate and have little meaning. For more information about floating inputs, see: Floating/Unconnected Analog Inputs (App Note)

Other considerations - some items are device specific, others not. Need to organize. Items: Stream (main), C-R during stream (main), floating inputs (might want high visibility, is main page too obscure?), connections (main, AIN applications; rename) , address steps (Modbus thing, out of place?), duplicate terminals (T7 only), calibration (main)

Calibration

T-series devices are calibrated during manufacturing. The calibration produces several coefficients which can be used to convert the binary results from the ADC to voltages. More about calibration can be found within the flash section here: 20.0 Internal Flash [T-Series Datasheet]

Volts vs Binary

The analog to digital converters in T-series devices always produce binary results. Those results need to be converted to voltages using the calibration coefficients and equations. That conversion can take place in the device or in the host computer. The location where calculations are performed depends on the communication mode being used and the selected register. The following list discusses the returned format based on (Communication mode, register) :

(CR, AIN#) - Voltage. When reading the AIN# registers through command response, the firmware on the device will convert the binary to a voltage before sending the result to the host computer.
(Stream, AIN#) - Binary. Stream produces too many binary results for the CPU on the device to convert them to voltage. To ensure that the device can sample at higher rates, binary results are always returned. When using the LJM driver, it will convert the results to voltages.
(CR, AIN#_BINARY) - Binary. Using the binary registers will instruct the device to always return binary.

For more information about communication modes see: 3.0 Communication [T-Series Datasheet]

Troubleshooting

We provide several guides which help users get the best results possible. This guide will help you find the right app note for your situation: Analog Input App Notes

Accessories

LabJack provides many accessories for signal conditioning and expanding the capabilities of T-series devices. For a complete list of available accessories see: https://labjack.com/collections/accessories