This road-test is a continuation from Keithley Bench Digital Multimeter - Review
Here I did some experiments to verify the core features of the Keithley DMM6500. These are some analog experiments to test the functionality.
dcv:dcv Ratio Measurements
This measurement will be done by applying the DC reference voltage to sense terminals and the voltage applied to the input terminals. Then the ratio is (DC signal voltage/DC reference voltage)
Since this DMM has no rear input scanner card I used the 2 channels on the front panel to calculate the dcv:dcv Ratio. At the front channels I used two LiPo batteries with similar charge DC voltage for measurements
The Test setup
By using the pinch and zoom I can see the irregular spikes in the LiPo battery DC voltage measurements
Measuring the DC value against a high quality Fluke Handheld DMM
Measuring the other LiPo Battery
The dcv:dcv Ratio Measurement of the two LiPo batteries as calculated above by the DMM
Check AC voltage at mains supply
This was pretty simple. I just popped in the DMM leads into one of the AC sockets to do the measurements
Fig: The DMM leads into the AC line
Fig: The correct output of the AC line in the house.
I also looked at the graphs here and let the measurement run for quite some time.
Measure capacitance
I selected an old unknown capacitance and used the smallest possible leads to the DMM input for doing capacitive measurement
Fig: The capacitor under test
Evaluating the graphs of this capacitance. As one can see this is not a very highly accurate capacitor and has been lying around for quite some-time.
Below I used capacitor in pF range to do the measurements. But of-course here the leads add to the parasitic capacitance of the measurement.
Fig: Measuring pF range capacitances. The average is 1.4 pF here
Measure Resistance
For this test I used a power resistor with high wattage and extremely low resistance of 0.05ohm. As one can see it below
Accurate low resistance measurements
The internal probe resistance
Here I have simply shorted the probes with each other to measure the internal probe resistance. I did use a metal crocodile clip so I will assume that the resistance of the clips adds to the probes as well. High quality probes have as low internal resistance as possible.
Fig: Low resistance of the probes in the range of 68 milliohm
Test diode functionality
Here the main aim is to test the functionality by forward biasing a diode and check for beep threshold and maximum resolution.
The diode test setup
Fig: How to test the pass fail of a diode with test current using DMM6500
Note: My initial aim was also to do 4 wire measurements but due to lack of the 4-wire measuring cable I was not able to do it. My future plan is to DIY a 4 wire cable and re-do some of the measurements.
Conclusion
As one can see from the above mini experiments that very accurate low current and low resistances can be measured with Keithley benchtop DMM. And the GUI is also very intuitive to use. The presence of on-screen graphs is very handy to make data-logging.
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