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  • 7 inch TFT color LCD screen
  • Ability to access additional (GL100) sensors & adapters
  • 20 analog input channels, expandable to 200 channels
    • All channels isolated
  • AC, DC, & rechargeable battery pack power sources
  • WLAN capable using optional WLAN Unit B-568
    • For remote monitoring and data logging
  • Smartphone access via GL-Connect app
  • Max sampling interval up to 10ms
  • Extend memory capacity with SD cards
    • Purchased separately, compatible up to 32GB
  • Flexible input system for a wide array of applications

What's in the Box

  • AC power adapter
  • Quick reference guide
  • Internal 4GB flash memory
  • Software & manuals (CD)
  • Calibration cert
  • 3-year warranty

The Graphtec GL840 data logger is a standalone multichannel data logger with isolated universal input. In addition to accommodating numerous measurements, the GL840 includes many communications options and advanced functions making it an incredibly versatile data acquisition instrument for a wide array of applications.

The GL840 has 20 analog input channels, isolated so that wiring errors or overloaded channels do not affect neighboring channels. The system is easily expandable to up to 200 channels by adding the optional B-566 terminal base unit and input terminal units (B-564 or B-565). Input terminal blocks can be connected directly via daisy chain or by using cable. This allows the input terminals to be placed in separate =locations depending upon the requirements of the application.

The GL840 has two SD card slots which support up to 32GB of memory which can hold over a year's worth of data depending upon the sampling rate. A full color, 7-inch TFT display allows user to view data in waveform or digital form while also displaying parameter settings.

The Graphtec GL840 includes a number of communications features which allows integration with other devices and easy file sharing. A wireless LAN module (B-568) can be added to connect the GL840 with Graphtec GL100-WL modules. This expands the measurement variety of the GL840 by utilizing sensors available to the GL100-WL which will relay data directly to the GL840. The GL840 can also be connected to a LAN via a WLAN access point. Measured data can then be monitored via a PC or smart device using the application software. Configuration can also be set via the network.


Graphtec B-513 Logic / Alarm Cable
Cable, 4 x Logic inputs & 4 x alarm outputs, 2 meters
In Stock
Graphtec B-514 DC Power Cable
2 meter DC power cable with bare ends for direct connection to DC power source
Graphtec B-567 Connection Cable
50cm or 2-meter cables for connecting the B-566 extension terminal base on the GL840 datalogger
In Stock
Graphtec GS-EXC Extension Cable
Extension cable for sensor input modules (1.5m long)


Graphtec B-530 Humidity Sensor
Humidity Sensor, 0 to 100% RH
Graphtec GS-TH Temperature / Humidity Sensor
Temp range: -4 to 185°F (-20 to 85°C), humidity range: 0 to 100% RH, for use with the GL100
Graphtec GS-LXUV Light & UV Sensor
Luminance (0 lux to 200k lux) and UV rays (0 to 30mW/cm2) dual sensor module, for use with GL100
Graphtec GS-3AT Acceleration / Temperature Sensor
Acceleration in 3-axis (maximum 10G), temperature 14 to 122°F (-10 to 50°C)
Graphtec GS-4TSR Terminal Adapter
Supports two optional thermistor types, terminal with up to 4 channels of temperature measurement
Graphtec GS-103AT-4P Thermistor Sensor
Normal type, sensor for GS-4TSR module, 3 m, 4 pcs/set, Temp range -40 to 221°F (-40 to 105°C)
Graphtec GS-103JT-4P Thermistor Sensor
Ultra thin type, sensor for GS-4TSR module, 3m, 4 pcs/set, temp range -40 to 248°F (-40 to 120°C)
Graphtec GS-DPA-AC AC Current Sensor
Measures current, power, accumulated electric power
Graphtec GS-AC Clamps
Ratings available: 50A, 100A and 200A
Graphtec GS-4VT Voltage / Temperature Terminal
4ch of voltage DC (20mV to 50V as well as 1 to 5V) and thermocouple (K or T type) temperature measurement


Graphtec B-569 Battery Pack
Battery pack, maximum 6 hours
Graphtec ACADP-20 Power Supply
Spare AC power adapter for GL220, GL240, GL820, GL840, and GL900 products


Please consider these optional accessories.

Graphtec B-568 Wireless LAN Module
Allows for Wireless Communications on Graphtec GL240 and GL840 Data Loggers
Graphtec B-564 Input Terminal
20-channel multi-input extension terminal for Graphtec GL840-M data logger
Graphtec B-566 Extension Terminal Base
20-channel terminal base for input terminals B-564 and B-565
250 Ohm Precision Resistor
Shunt resistor for DC current input
Graphtec GS-DPA Dual Port Adapter
Graphtec GL840 Pelican Case
Pelican Polypropylene case with foam inserts cut to fit and protect your GL840 data logger
In Stock

Application Notes

Here's how some of our customers used this product.

Creating Temperautre Maps

The Background: A consumer electronics company is creating a temperature map as part the development of a new product.

The Problem: Temperatures are taken at 27 points on the test surface. To identify emerging trends, the customer wants to log all the measurements.

The Solution: The Graphtec GL840 was paired with 27 Watlow thermocouples to create the matrix used for temperature measurement. The GL840 has 20 input channels and can be expanded to up to 200 channels. Multiple communications options make it easy to transfer data for analysis.