RLC meter simulation - Page 1
Forum section: electronics / projects

author: emna
author_rank: Newbie
timestamp: January 16, 2017, 12:47:59 pm
content: Hello,I am trying to simulate this using ISIS Proteus:https://www.eevblog.com/forum/projects/rlc-meter-simulation/?action=post;msg=1114657#https://www.eevblog.com/forum/projects/rlc-meter-simulation/?action=post;msg=1114657#I read one document about this but I can't figure out why he is generating a square wave ( using the pic16F876A at pin 13) with a frequency of 10KHz, 100 KHz or 1 MHz and he divide it by 100 to get the needed test signal frequency ( 1KHz, 10KHz or 100KHz) and than he need to multiplie this frequency again by 100. why he don't generate with the pic the (( 1KHz, 10KHz or 100KHz) square wave signal ?for more details you can chech this:I have an other question for the simulation, I am using ISIS Proteus: I need the 8th-order low pass elliptic switched- filters: MAX293 but I can't find it. I tried to use an other filter that exist in isis library but I can't find any one. If any one have the library or a link for it or any other suggestion plz help me !

author: DmitryL
author_rank: Regular Contributor
timestamp: January 16, 2017, 01:41:14 pm
content: Why do you want to simulate this device ? It just works out of the box, trust me..

author: jm_araujo
author_rank: Regular Contributor
timestamp: January 16, 2017, 02:55:15 pm
content: I think it divides the frequency generated as a mean to create a quadrature (0º + 90º) signal. I'm not sure you could generate them both with the required precision in the micro-controller.As far as multiplying, it seems to me that it's amplification and not in frequency domain!

author: DmitryL
author_rank: Regular Contributor
timestamp: January 16, 2017, 03:26:28 pm
content: In order to make proper phase measurements (BTW, test frequencies are 100Hz, 1Khz and 10 Khz), this device uses a single clock source for following purposes:- quadrature sampler- Square wave generator (after filtering by that 8-th order filter and some commutated on demant analog filters it becomes a sine for generating current that goes to DUT)- digital filter (chip from Maxim)Despite that all these filters shift signal phase regarding to the sampler uses, this difference is always constant for the selected frequency range. And it is taken into account whiledoing device Open/Short/Load calibration .

author: Kleinstein
author_rank: Super Contributor
timestamp: January 16, 2017, 04:59:17 pm
content: The switched capacitor filter (MAX293) needs the higher frequency (100 times signal frequency) to set the filter frequency. Dividing the frequency down it rather simple. This also gives access to an exactly 90 degree phase shifted signal. There is no multiplication of the frequency.Today one would use a different technique, with less analog and more jobs done by the µC.

author: emna
author_rank: Newbie
timestamp: January 17, 2017, 12:40:20 pm
content: Dear all,Thank you for your answers. now it's more clear.@Kleinstein: I will use a µC also for some tasks:Generation of signals and the synchroneous detection. If you have an other suggestion let me know

author: Kleinstein
author_rank: Super Contributor
timestamp: January 17, 2017, 01:24:09 pm
content: Whenn using a µC, there is the option to use a kind of software driven DDS and also synchronous sampling with the ADC and thus also do the synchronous detection in the µC. This is especially true for the lower frequencies.As some µCs allready include an DAC, this reduces the external analog part quite a lot: fixed reconstruction filter (no more filter adjustment), no more external ADC. As the hardware is more like a low frequency vector network analyzer one could also use more complicated models as simple RC, LR or R.