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Script to Measure Power using the DC Voltage Ratio Function

DMM6500 6½-Digit Touchscreen Multimeter
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Joined: July 16th, 2018, 5:31 am
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Script to Measure Power using the DC Voltage Ratio Function

Post by akirby » October 22nd, 2018, 10:57 am

This script for the DMM6500 allows for power measurements to be made using the DC Voltage Ratio function. It requires a low ohm shunt resistor to be placed between the Sense terminals. The user can specify the exact value of the shunt resistor by changing the "shuntValue" variable in the script.

1. Download the attached .tsp file
2. Make sure your DMM’s command set is set to TSP in MENU > Settings
3. Put the script on a USB drive and insert into the DMM
4. Press MENU then touch "Run" in the "Scripts" column
5. Select the script named "MeasurePower.tsp"
6. Click "Run Selected"

The script leverages the fact that the Ratio function stores a voltage measurement for both Sense and Input voltages in a single reading, displaying Input voltage over Sense voltage. If we use a shunt resistor across the Sense terminals, we can measure current because we know the shunt resistor value and we measure the voltage across the resistor. The Sense voltage value is stored in the extra field of the buffer, so we make the reading buffer a "Full" style buffer to include this value. The shunt resistor value is divided out of the Sense voltage measurement according to Ohm's law, giving us a value for current. The Sense voltage is also multiplied out of the Ratio measurement to get Input voltage. The two are then multiplied together to find power and the result is stored in a writable buffer, which is shown on the instrument's screen. The timing and number of measurements can be adjusted by changing the "timeBetween" and "readings" variables in the script.
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