Tektronix Technical Forums are maintained by community involvement. Feel free to post questions or respond to questions by other members. Should you require a time-sensitive answer, please contact your local Tektronix support center here.

Script to Measure Power using the DC Voltage Ratio Function

DMM6500 6½-Digit Touchscreen Multimeter
Post Reply
Posts: 1
Joined: July 16th, 2018, 5:31 am
Country: United States

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.
terminals.png (13.15 KiB) Viewed 4119 times
(1.16 KiB) Downloaded 725 times

Posts: 1
Joined: September 16th, 2020, 4:31 am
Country: Romania

Re: Script to Measure Power using the DC Voltage Ratio Function

Post by andrei_ser » September 16th, 2020, 4:37 am


Starting from the indicated procedure for measuring power using the DC Voltage Ratio function, I would like to know how will be possible to use 2x DMM6500 units, both configured in the same way (meaning using the DC Voltage Ratio function), and to collect data from the input and the output of a DC-DC Converter.

The application is to measure the DUT's efficiency (output power vs. input power).

Is it possible also to provide a script that could be used to perform such a measurement?

Thank you very much!

Andrea C
Keithley Applications
Keithley Applications
Posts: 1466
Joined: October 15th, 2010, 10:35 am
Country: United States

Re: Script to Measure Power using the DC Voltage Ratio Function

Post by Andrea C » September 22nd, 2020, 6:47 pm

Interesting idea. The ratio function applied with the shunt effectively gives you a watt meter.
For DC-DC converter efficiency, you’d still need a power source for the input and some loads on the output.
How many load conditions would you want?

Could be more straightforward to use power supply with 6.5 digit measurements for input (model 2280S), and a SMU as the load inducing watt meter on the output (model 2450 probable). The 2450 could control the 2280S over LAN and our TSP.NET.

Post Reply

Return to “DMM6500 Bench/System DMM”

Who is online

Users browsing this forum: No registered users and 1 guest