Products > Test Equipment
TH2830 vs TH2832
mawyatt:
--- Quote from: nctnico on July 28, 2023, 09:00:27 am ---
--- Quote from: mawyatt on July 25, 2023, 02:22:21 pm ---One of the benefits (not usually mentioned) of these LCR meters is the lower Z ranges, like DCR at 1 Ohm and ACR 3 Ohm ranges, where the DUT current can be as high as ~67ma. These ranges are below most quality DMMs like the KS34465A (100 ohms) and DMM6500 (10 ohms).
--- End quote ---
That statement may not be true as the 6.5 digit DMMs you mention have a lot higher accuracy compared to an LCR meter and you might be operating the LCR meter outside the range where it is most accurate when measuring low resistance values.
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Well it is true regarding the KS34465A vs Hioki IM3536 measuring below 100 milli-ohms, the KS spec per performance verification is an error within 4 milli-ohms after 24 hours, 3 milli-ohms within 24 hours on the lowest 100 ohm range. The IM3536 is a worst case 1% error of range at 100 milli-ohm range as base line specification, or 1 milli-ohm max error in 100 milli-ohm range.
The KS is fundamentally a more overall precise instrument for DC resistance measurements, however at the lowest range on the KS is 100 ohms, whereas the lowest range on the IM3536 is 100 miili-ohms, a thousand fold lower full range. One reason we acquired the Keithley DMM6500 was for the lower 10 ohm range, also the TH2830 has a 3 ohm DCR Range.
We haven't done much low resistance comparisons, but did find a note from 10/15/21 where we compared the TH2830 with the newly acquired DMM6500 and the KS34465A (didn't have the IM3536 then). The resistor was a Vishay 0.12 ohm that measured 0.120560, 0.12056 and 0.1197 ohms on the TH2830, DMM6500 and KS34465A respectively.
Anyway, for very low ohms measurements where the LCR meter utilize a much higher test current (KS uses just 1ma) and a much lower full scale range, we'll lean towards the LCR readings if the measurements differ much between the DMMs and LCR readings.
Of course the type and use of the precision Kelvin clips likely has more user induced error than the instruments themselves at these low R ranges :o
BTW one shouldn't discount these modern bench type LCR meters regarding overall accuracy and ability to resolve small impedances. Likely they employ the modern single chip SD 24 bit ADCs, like some of the newer DMMs do, which are quite remarkable in achieving performance levels usually attributed to more complicated and costly full circuit designs.
Best,
Martin72:
--- Quote from: Martin72 on July 28, 2023, 02:26:36 am ---XL is the reactance of the coil:
XL= 2*pi*f(Hz)*L(H)
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Today I measured the 1µH coil from my DMMCheck unit with our ST2830 at work, then calculate by hand with a calculator whether the displayed values are consistent.
XL = 2pi*f*L = 6.28*100khz*1.0235µH = 0.643 Ohm
Impedance Z = SQR R²+X² = SQR 0.09696²+ 0.64303² = 0.6503 Ohm.
Well, they are...
And this was just for fun. 8)
KungFuJosh:
This is kinda awesome... I made a 2nd version of my meter reference board, but this version uses 4mm pads, and I added 3 separate individual kelvin tests for low value L, C, and R. I slapped in a 10nH to test, and it worked!
mawyatt:
That's impressive being able to measure 10nH with Kelvin Clips, would think the cable and clips themselves would limit lower inductance measurements. Did you Open/Short calibrate using the pads?
Also, were you able to measure the 10nH in your SMD fixture? Would think this would give more repeatable results than Kelvin Clips and mounted SMD device.
Best,
KungFuJosh:
--- Quote from: mawyatt on August 22, 2023, 03:11:01 am ---That's impressive being able to measure 10nH with Kelvin Clips, would think the cable and clips themselves would limit lower inductance measurements. Did you Open/Short calibrate using the pads?
Also, were you able to measure the 10nH in your SMD fixture? Would think this would give more repeatable results than Kelvin Clips and mounted SMD device.
Best,
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The cables are definitely a limiting factor. I had to perform short calibration a few times to get them to a good place. The key was to check that the short read close enough to zero once switching back to the measurement screen. For those measurements, short read around 0.5nH, which was close enough for me. Some methods of shorting (including shorting to themselves) left the zero measurement off by way too much to be useful for anything in the low nH range. Self shorting gave very inconsistent results.
Making sure the clips were well connected, without physical interference was also important. That's why the PCB is elevated in the photo. I also had to put a tiny drop of solder on the test pads so the clips could hold on well, without contacting too much of the board.
I left the clips connected for a while to see how stable it was, and it averaged around 9.5nH (attached).
Yes, the SMD fixture works for 10nH. However, I hate using the SMD fixture for reference testing. It takes hours to go through components individually with the SMD fixture. I can blow through this PCB really fast with the kelvin clips. Nothing needs to be perfect for me, it simply has to show it's close enough in a given range. These tests have shown where the firmware issues still exist, which thankfully isn't so much anymore.
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