Products > Test Equipment
Princeton Applied Research 160 Boxcar Integrator
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ch_scr:

--- Quote from: wishboneash on August 24, 2022, 07:56:44 pm ---
--- Quote from: ch_scr on August 13, 2022, 08:01:46 am ---Thank you for the demonstration of the device. To me it seems like, for the case of a single sine component, it is done today with fft on a scope? But with a complex waveform, this technique shows it - very impressive.
Regarding the red and blue "time constant" dials, the aperture time selector ring above them has markings in red and blue as well. I belive with longer aperture times, the lower red dial is used instead of the blue one. They probably select RC components mounted directly to wafer switches - the need for two dials might come from limits of physical construction.

--- End quote ---

Ah, yes. That makes sense.
I did find an abbreviated datasheet/manual online which describes this as normal resolution and high resolution mode related to the aperture time.

I am still amazed at how cleanly it rejects uncorrelated signals. The analog meter beats any digital output and this works real time as well without any programming. Moreover, the analog output can be captured and post processed further. For the price, it's unbeatable!
Thanks.

--- End quote ---
There is a "Model 162 Boxcar Averager" that seems similar in function, it has a detailed manual over there that contains schematics and descriptions. Could you do a small teardown of your device and share pictures of the insides? It might shed some light on how similar the devices are.
wishboneash:

--- Quote from: ch_scr on August 24, 2022, 08:38:16 pm ---
--- Quote from: wishboneash on August 24, 2022, 07:56:44 pm ---
--- Quote from: ch_scr on August 13, 2022, 08:01:46 am ---Thank you for the demonstration of the device. To me it seems like, for the case of a single sine component, it is done today with fft on a scope? But with a complex waveform, this technique shows it - very impressive.
Regarding the red and blue "time constant" dials, the aperture time selector ring above them has markings in red and blue as well. I belive with longer aperture times, the lower red dial is used instead of the blue one. They probably select RC components mounted directly to wafer switches - the need for two dials might come from limits of physical construction.

--- End quote ---

Ah, yes. That makes sense.
I did find an abbreviated datasheet/manual online which describes this as normal resolution and high resolution mode related to the aperture time.

I am still amazed at how cleanly it rejects uncorrelated signals. The analog meter beats any digital output and this works real time as well without any programming. Moreover, the analog output can be captured and post processed further. For the price, it's unbeatable!
Thanks.

--- End quote ---
There is a "Model 162 Boxcar Averager" that seems similar in function, it has a detailed manual over there that contains schematics and descriptions. Could you do a small teardown of your device and share pictures of the insides? It might shed some light on how similar the devices are.

--- End quote ---

Sure, I can look into doing a teardown of the 160. I had seen the 162 manual before, it appears to be modular like the Stanford Research ones.
garrettm:
These old boxcar integrators are pretty neat. After watching wishboneash's demo, I found the scan option (sweeping of the sampling window) to be the most interesting feature.

In this mode, the boxcar essentially acts as a sample-and-hold circuit. This would allow a slow, but high resolution digitizer (like a 6.5 digit DMM) to sample the signal for high fidelity reconstruction. In this way, fast, repetitive AC signals can be digitized using a slow DC voltmeter. I'm curious if this method could be used for high accuracy AC voltage measurements?

At any rate, it’s possible that, for the price, an old boxcar integrator and benchtop multimeter can outperform most fast digitizers sampling at >= nyquist frequency even with significant averaging. It would be interesting to do a comparison and determine the ENOBs for each setup.
wishboneash:

--- Quote from: garrettm on August 25, 2022, 06:13:28 pm ---These old boxcar integrators are pretty neat. After watching wishboneash's demo, I found the scan option (sweeping of the sampling window) to be the most interesting feature.

In this mode, the boxcar essentially acts as a sample-and-hold circuit. This would allow a slow, but high resolution digitizer (like a 6.5 digit DMM) to sample the signal for high fidelity reconstruction. In this way, fast, repetitive AC signals can be digitized using a slow DC voltmeter. I'm curious if this method could be used for high accuracy AC voltage measurements?

At any rate, it’s possible that, for the price, an old boxcar integrator and benchtop multimeter can outperform most fast digitizers sampling at >= nyquist frequency even with significant averaging. It would be interesting to do a comparison and determine the ENOBs for each setup.

--- End quote ---

Yes, I assume one could reconstruct or measure AC waveforms as I showed, as long as the AC signal is repetitive (any complex waveform) and the long term clock jitter is small. I hope to do some experiments for low and high frequency AC signals.
wishboneash:
I did a teardown of the PAR 160 which can be viewed here -  https://youtu.be/zGFD-I0_4gY. It appears to be quite different from the 162 (looking at its manual). This one is built up using a whole slew of boards plugged into slots and highly modular. Unfortunately, I couldn't shed much light on the details of the cards without a proper service manual except to guess about some basic functions.
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