KS34465A and DMM6500 Cap Measurements

[mawyatt]

Decided to check how the KS34465A and DMM6500 compare when making capacitive measurements. Used a Tonghui TH2830 LCR meter as the "reference", and picked COG SMD, Tanalum SMD and leaded Mica, Polystyrene, and Polypropylene types. Did not include Electrolytics, nor Mylar, nor High Dielectric ceramic types because on the long wait for stabilization.

To help make the comparison we decided to use the standard Leaded Device and SMD Fixtures utilized with Lab Type LCR meters. Since the DMMs use 2 wire sensing a BNC to Clip lead cable with BNC to Banana adapter was used. For mating with the fixtures a pair of BNC socket panel connectors were inserted into the Fixtures LP and HP BNC connectors, and the clip leads attached and were taped down to prevent movement.

The Null feature was used on the KS to remove the residual fixture and BNC cable capacitance, as was the Relative Value feature on the DMM6500. Both meters were using MX+B and Statistics Math Functions.

The technique utilized in these meters performed well relative to the TH2830 which utilized a Synchronous Sampling of a sine wave technique, common to most lab quality LCR meters.

Anyway, we don't have any reservations using the Cap feature in these quality DMMs for a quick evaluation in the lab.

Best

[Kleinstein]

The largest differences are with the mica and tantalum capacitors. These are the 2 types with somewhat larger loss and thus a more frequency dependent capacitance than the low loss NP0, PS and PP types.
It would make sense to know the frequency that the DMMs are using. Especially with capacitors with loss, like mylar, mica and even more the electrolytics (inlcuding tantalum) a high resolution for the capacitance only makes sense when comparing at the same frequency.

[HKJ]

It would make sense to know the frequency that the DMMs are using. Especially with capacitors with loss, like mylar, mica and even more the electrolytics (inlcuding tantalum) a high resolution for the capacitance only makes sense when comparing at the same frequency.

DMMs are generally not using a frequency, but instead using charge/discharge cycles. This means the actual charge/discharge frequency will vary depending on capacitance and me be down to a few Hz and even lower for large electrolytic capacitors.

[mawyatt]

The DMM6500 waveform is smaller in amplitude than the KS34465A, much smaller on larger capacitance DUT. Both appear to be a constant current drive signal into the capacitor DUT, however the KS34465A introduces a DC offset on larger capacitance DUT, the DMM6500 does not. The linear voltage rise across the DUT due to the constant current is followed by an exponential decay as with a simple resistive discharge. Both seem to have the DUT with a repeating waveform which has a frequency that varies somewhat inversely with DUT capacitance.

After observing the waveforms from both with varying capacitor DUT, the algorithm/method is entirely different between the KS and DMM. With a 10nF, the DMM/KS frequency is 455/38Hz, with 0.47uF 93/5Hz, with 22uF 11/2Hz.

To add to HKJ, these DMMs utilize an algorithm/method where the frequency and amplitude varies with DUT capacitance with a unipolar relaxation type waveform, whereas an LCR has a fixed amplitude and frequency with a bipolar sinusoidal waveform, completely different measurement methods and waveforms, and why we mentioned "The technique utilized in these meters performed well relative to the TH2830 which utilized a Synchronous Sampling of a sine wave technique, common to most lab quality LCR meters."

Best,

[mawyatt]

Added some waveforms across the DUT by the KS and DMM. Note the vertical and time scale factors and the -3V offset on some of the KS displays.

#4 KS 22uF Electrolytic
#5 DMM
#6 KS 100uF Electrolytic
#7 DMM
#8 KS 10uF Mylar
#9 DMM
#12 KS 1uF Mylar
#16 DMM

[mawyatt]

And a few more. Note the expanded version which changes the vertical and time scale factor between the KS and DMM.

#17 KS 1nF Polystyrene
#18 DMM
#19 DMM Note Expanded Scale
#20 KS 100pF Mica
#21 DMM
#22 DMM Note Expanded Scale

Best,