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GP-HR Resistance Application Notes
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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.

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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

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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.

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Click on the Write Unit, Scaling and Calibration values to the Logger button to send the new settings to the logger.

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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

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