Precision LCR meter at 10Vrms - Page 1
Forum section: electronics / general

author: tcsaba101
author_rank: Contributor
timestamp: December 15, 2018, 08:24:18 am
content: I have a friend who experimenting for 10+ years to measure stress situation of living plants.In laboratory testing they are using a GW8101 (https://www.gwinstek.com/en-global/products/detail/LCR-8000G) for measuring the capacitance of the root mass.In field they use an Keysight U1733 Handheld LCR meter.See the enclosed picture, or read this publication for deeper understanding:http://real.mtak.hu/73723/1/fpls_09_00093_u.pdfNow they are experimenting in the field, and for precision measurements they would need an instrument like the GW8101, weather proof, and providing up to 10V signal for measuring.The frequency requirement 100Hz - 100kHz, sweep mode.Any idea of existing product or a project what can be used as source to develop one?

author: Kleinstein
author_rank: Super Contributor
timestamp: December 15, 2018, 09:08:23 am
content: Why would one need such a high output level. It is probably already difficult enough to understand the small signal behavior or the roots. I would imagine there could already be some damage to the plant at that much current.The high amplitude makes it rather difficult to find an instrument. Otherwise it is something like an impedance analyzer - though they are usually bench-top and not portable. So something like the Bode100 that Dave showed in a video some months ago. If one could live with a slightly lower upper frequency limit there may be audio analyzers that might work up to maybe 50 kHz.A starting point for a development could be something like red pinta or the analog discovery. One of those outdoor laptops might also be an option if the audio frequency range is sufficient.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 15, 2018, 02:41:43 pm
content: The machines that will do that tend to be quite expensive. The Keysight E4980A would be a good candidate, but they run about $16K. IET Labs makes a similar unit for a bit less. If you don't mind manual measurements, some old mechanical bridges will do it, but the higher frequencies are a bit of a problem. Most only go to 10kHz or so. The venerable GR 716-C can do it easily, and can probably be had for cheap, but you'll need a generator and detector to make it work. Most people don't have the space or patience for it. There's probably some Arduino/Basic Stamp/Teensy Board solution that could be rigged up for way less money but more effort. Have a look at the Teensy 3.6, an amazing amount of features in an easy to use package. Also seehttp://njhurst.com/blog/01356576041andhttp://ecad.tu-sofia.bg/et/2014/ET2014/AJE_2014/170-N_Djermanova.pdf

author: tcsaba101
author_rank: Contributor
timestamp: December 15, 2018, 08:25:10 pm
content: Thanks, Kleinstein!I can not comment the 10V requirement. Maybe it is high.What I know they think they need more than 2V.I just wrote down what I have got.

author: tcsaba101
author_rank: Contributor
timestamp: December 15, 2018, 08:46:35 pm
content: Quote from: Conrad Hoffman on December 15, 2018, 02:41:43 pmI couldn't find the Teensy example.Studying the ADS5933 it could work.An amplifier on the VOUT increasing the output level.The proper RFB, to set back the level, (maybe multirange) could be a solution.Encapsulated in a IP68 case, equipped with LoRa or GSM transmitter could do the job.