LCR Meter for measuring Diode Junction Capacitance - Page 1
Forum section: electronics / testgear

author: deadly_penguin
author_rank: Contributor
timestamp: October 14, 2025, 10:08:24 am
content: So, I need to measure junction capacitance (with bias) and shunt resistance of some prototype photodiodes for $dayjob and I'm shopping for LCR meters.I'm looking between the Hioki IM3536, B&K BK895, and the R&S LCX200 - they all look like they should have reasonable relative accuracy for ~10-100pF (better than the old Wayne Kerr we found in a bin, anyway), they're all within my ~£10k budget including some test fixtures and leads, and they're all just about quick enough to be generally useful outside this single project.Does anyone have any particular suggestions?

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 14, 2025, 12:12:14 pm
content: If DC biasing is important: The LCX200 seems to be able to provide the largest internal bias voltage (up to 10 V) of the three units, and can accept an externally supplied bias voltage up to 40 V.

author: EC8010
author_rank: Frequent Contributor
timestamp: October 14, 2025, 12:58:25 pm
content: The Hioki only goes up to 2V or so. But it can do 1MHz, which makes measurement easier. I have previously used a Hameg 8118 at 100kHz to measure diode capacitance and I made an external box to allow me to measure some silicon wafer detectors up to their full depletion voltage of 70V. I think the LCX200 is a newer version of the 8118, with a greatly inflated price tag.By the way, I have a Hameg 8118 on sale for £750 (in the Buy/Sell/Wanted section) and could throw in the box for measuring detectors. It's up for sale because I now have an IM3536. PM me if you're interested.

author: chilternview
author_rank: Frequent Contributor
timestamp: October 14, 2025, 02:19:50 pm
content: You don't specify what bias voltage maximum you need, or the frequency (but for 10-100pF you'd need 1MHz ideally).The Keysight E4980A will do +/- 40v internal dc bias. Or Tonghui make a range of LCR meters, the dc bias is a bit more limited though (+/- 5v I think); the BK895 is a rebadged Tonghui.

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 14, 2025, 02:23:23 pm
content: That BK model is a TongHui rebrand, and more expensive. However, you'll get much better support from BK. You can also countact Sourcetronic for their version of the same LCR meter. TongHui's fixtures will support 40V external bias.The IM3570 is another model to consider if you're looking at the LCX200. To match the features of the IM3570, the LCX200's price jumps much higher.

author: mawyatt
author_rank: Super Contributor
timestamp: October 14, 2025, 02:43:14 pm
content: We have and use the Hioki IM3536 and Tonghui TH2830, both acquired new awhile back for a project where we had to have known accurate results.The IM3536 just does everything well, goes from 4Hz to 8MHz, has high DUT current (>100ma, good for low Z) and has a low voltage DC bias built-in. However, the fan sounds like a jet engine....and this isnormal!!The TH2830 is good, does everything well and the fan is quiet. However, it's limited to just displaying 2 parameters, no DC Bias and works from 50Hz to 100KHz. The more expensive TH2832 has built in DC Bias and goes to300kHz200kHz.As mentioned, for low capacitance measurements, higher frequency measurements are preferred, and we use the IM3536 more often.For external DC Bias we've created a custom fixture adapter which allows much higher applied voltages and successfully measured some PN junctions vs DC Bias in the pF regions. We've also created some simple routines that allow plotting multiple parameters, if you search you'll find some of this.Best

author: Kleinstein
author_rank: Super Contributor
timestamp: October 14, 2025, 03:10:55 pm
content: If one wants to measure capacitance also at low voltages (often wanted to analize the junction) one also has to make sure the AC test voltage is small (e.g. 100 mV). A large AC voltage can be an issue for a highly nonlinear capacitance.

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 14, 2025, 05:19:27 pm
content: Quote from: mawyatt on October 14, 2025, 02:43:14 pmThe TH2832 goes to 200kHz. Also, the TH2830 can be easilyimprovedto the ST2832.

author: deadly_penguin
author_rank: Contributor
timestamp: October 15, 2025, 10:26:15 am
content: Thanks all for the responses - I think I've managed to sell myself on one of the Hiokis and an external bias if I need a bit more than the internal 2.5V.