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GP-HR Voltage Application Notes
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Any combination of the three analogue inputs of the GP-HR Logger can be configured to read Voltage. If the voltage to be logged is less than 2.048 volts, no additional components are required. A Breakout Probeset B-PS could be used to connect the logger to the voltage sources.

The voltage  can be connected directly between:

If a voltage greater than 2.048 volts is to be logged, a resistive voltage divider will be required.

We manufacture voltage dividers that are built into the GP-HR 6 pin Plug. The 3 inputs can be any combination of 2.5V, 5V, 6V, 9V, 10V,12V, 15V, 18V, 24V, 28V, and 32V
V3-PS Voltage Divider Probeset  

The following information is provided for users who wish to make their own voltage dividers.

For high accuracy applications, resistors should be 0.1% ± 25ppm/° C.
These are available through Farnell and RS

For lower accuracy applications, cheaper 1% ± 50ppm/° C can be used.
For example, the Philips MRS16T series available from Farnell.

Circuit for a resistive voltage divider

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Nominal Prefered Prefered Actual
Input Value R1 Value R2 Fullscale
2.5V 22k 75k 2.6V
5V 62k 39k 5.3V
6V 68k 33k 6.3V
9V 82k 22k 9.7V
10V 62k 15k 10.5V
12V 75k 15k 12.3V
15V 68k 10k 16.0V
18V 82k 10k 18.8V
24V 75k 6k8 24.6V
28V 91k 6k8 29.5V
32V 100k 6k8 32.2V
40V 91k 4k7 41.7V
50V 82k 3k3 52.9V

Circuit for GP-HR with 3 voltage divider inputs

volt_divider_circuit_diagram2.gif (5726 bytes)


It is preferable that no part of the circuit is connected to mains earth while the logger is connected to the computer as this may cause ground loop currents.

If the input voltage is floating with respect to mains earth then no precautions need to be taken when connecting the logger to a computer.

Setting up Voltage channels using the OmniLog Software

Connect the GP-HR logger to a computer and Run the OmniLog software

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 Volt option as shown

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Notice that after the Volt probe has been chosen the Units in the Unit and Scaling box has been set to V

Now give the Channel a meaningful Long and Short name in the Logger Channel Name box as shown below

omni_setup_mA2.gif (16884 bytes)


If you are using a voltage divider, select the value of the Voltage divider from the Select Button in the Units and Scaling box as shown.


omni_setup_volt3.gif (19011 bytes) 

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

If you wish to calibrate the Voltage channel at this point, follow the calibration procedure in the OmniLog Help User Manual. You can see this procedure by clicking on the Calibration Notes button in the Calibration box.

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