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| Tutorial, Teardown & Experiments with Stanford Research SR530 Lock-in Amplifier |
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| Hugoneus:
--- Quote from: Kleinstein on September 05, 2017, 05:40:18 pm ---A lockin is a really powerful instrument. The two experiments are really nice. However the time constant at the Lockin is chosen rather long - thus a sluggisch response. It could have been done with faster response - despite of increasing noise. It might have been interesting to also look at the monitor output for the second experiment. This might have even replaced the measurement with the DMM. The SR530 is still a classical analog one. Modern Lockins usually do much of the operation in digital - so the block diagram looks different. I am somewhat surprised the SR530 did not include an internal function generator. Usually there also is a simple generator included. --- End quote --- It does have an internal oscillator! I just didn't use it to avoid causing confusion. The internal source is accessible from the back. |
| Kleinstein:
If one has time, one can really go down in bandwidth and this way down in noise. I have once used a similar lockin with additional external digital integration over 1000 seconds to look at a really small signal. It just took a weekend to get a curve. Using digital integration (e.g. reading via GPIB) can cut down on the waiting time for the signal to stabilize, so less time is lost. For an experiment like the laser - LED one, the better mode is to use just one channel and adjust the phase before. Using the amplitude / phase modes is kind of easy to use, but gives slightly higher noise. So this experiment could also be done with a simpler single channel version if the lockin. The dual phase version has very little advantage in this case. |
| SilverSolder:
Awesome video. Is there a schematic available for this instrument? |
| wishboneash:
Looking for the schematic myself. I have a big error in the current gain (around 20-30%) but voltage gain is fine (a few percent error at most). The description from the manual states - <<When the input selector is set to current, the input to the pre-amp comes from the output of the current to voltage converter, 1/2 U102. U102 is a low voltage-noise bipolar op amp. Q102 serves as an input buffer to provide low current-noise to the input. The op amp always maintains a null at the gates of Q102 thus providing an input impedance of 1KΩ (R128). The input current is converted to a voltage by R135 and the op amp. Q103 bootstraps out the summing junction capacitance of Q102.>> Seems like the 1kohm is a terminating impedance and input current is buffered by an N ch FET and sent to a TIA with a feedback gain of 1e6 (R135). I'll open it up and see if I can find out what's going on. |
| _Wim_:
This documents included the schematic of the SR510, which should be fairly similar. Not the best scan, but better than no schematics... Had to split the zip in 4 parts to attach it here. Files named Lockinamplifier_SR510.z0x.zip need to be renamed to Lockinamplifier_SR510.z0x to unzip (forum only allows to attach zip files) |
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