GP-HR Resistance
Application Notes

Any combination of the three analogue inputs of the GP-HR Logger can be configured to read Resistance. A load resistor is required in series with the unknown resistance.
The unknown resistance (R2 in diagram) is placed between
any one of the analog inputs (Pin 2,3,or 4) and common (Pin 6).
The load resistor (R1 in the diagram) is placed between the
analog input used by the unknown resistance and the switched supply (Pin 1) .
We recommend the use of a 15K to 100Kohm load resistor.

Setting up Resistance channels
using the OmniLog Software
Connect the GP-HR logger to a computer and Run the OmniLog
software (Ver 1.34 or greater)
From the Logger
Control Screen select Channel and Probe Setup
Select the Channel that you wish to setup (Ch 1, 2 or 3)
From the Probe box select the Resistance option as shown
Notice that after the Resistance probe has been chosen the Units in the Unit and
Scaling box has been set to K ohms
If you wish to display in Ohms or Mohms click on the Select Button in the Units and
Scaling and select Ohms or Mohms.
Next measure the exact actual resistance of the Load
resistor in Kohms with a accurate resistance meter (resistor disconnected from the logger)
and enter this value in the Calibration
Offset box. eg
If the load resistor is 118.23Kohms enter 118.23 in the Offset area of the Calibration Box as shown.
Click on the Write Unit, Scaling and Calibration values to the Logger button to send the new settings to the logger.

Typical Experimental Test Results using a 15K load resistor
Actual
Resistance |
Logger
Display |
|
100ohm |
0.1K |
|
220ohm |
0.2K |
|
560ohm |
0.5K |
|
820ohm |
0.8K |
|
1K |
1.0K |
|
2.2K |
2.2K |
|
4.7 |
4.6K |
|
8.2K |
8.1K |
|
10K |
9.9K |
|
22K |
21.9K |
|
47K |
46.9K |
|
82K |
82.2K |
|
100K |
100.1K |
with less than .1K noise |
470K |
480.3K |
with ± 2K noise |
1M |
974.2K |
with ± 12K noise |
