And since multiplying two signals at the same freq but at a 90 deg offset results in an average of zero, you would also multiply your signal with a copy of the reference but at 90 deg offset, and thus results in I and Q outputs
Jason, Sure I recall. I dont think that Keithley ever offered a Lock-in, but if they did I think it would have been a good one based on their other offerings.
@@markschnittker4770 Nice to catch back up. No. They don't. I'm with Lake Shore Cryotronics and the new M81 does have lock in measurements: www.lakeshore.com/products/categories/overview/material-characterization-products/measureready-m81-synchronous-source-measure-system/measureready-m81-synchronous-source-measure-system?M81-Branded&M81&hsa_kw=m81&hsa_mt=p&hsa_tgt=kwd-389603167127&hsa_src=g&hsa_ad=632730062849&hsa_ver=3&hsa_cam=18806881853&hsa_net=adwords&hsa_acc=3884305122&hsa_grp=143470127415&gclid=EAIaIQobChMIltWFoPDq_AIVJcmUCR0ypgrSEAAYASAAEgKbdPD_BwE
Increasing the time constant will average out the lower frequency components. This is analogous to narrowing the bandwidth of the frequency range that will pass through.
The chip is the AD630, but many companies make low cost lock in amplifier boards from the AD630 chip and simply call them an AD630 lock in amplifier. I have purchased them from Ebay and Amazon. If you do a web search I am sure you will find some. Note that they are not nearly as sensitive as a bench top tool and also they are not adjustable for phase or time constant, but they do work quite well if your signal only 2-3 orders into the noise. If your signal is 6 orders below then noise, then you would probably need the much more expensive SRS lock-ins. If you get a chance to use an SRS, then you will find they are fantastic tools which cost much more, but are 3-4 orders of magnitude more sensitive than an AD630 lock in.
