"Electrometer amplifier" to measure very low currents using a very, very low bias current op amp. Used in instrumentation. It is the feedback resistor in a current to voltage circuit.I am wondering about what the application of such a resistor would be.
I am building a capacitor tester.I am wondering about what the application of such a resistor would be.
That will be a very interesting device when it i completed. Years ago I studied the plans published for "the femtofarad Meter" as part of a work project. But we needed to measure dielectric absorbtion and its variation and changes with aging and temperature. So measuring capacitance was not enough, nor was measuring leakage current.I am building a capacitor tester.
front end of charge-coupled preamps.
Is damp air/high humidity a problem? Does the whole amp need to be in a perfectly clean and dry environment?We commonly use 1GΩ encapsulated in glass in the front end of charge-coupled preamps.
Those are for current sense, so they are mΩ(m=0.001), not MΩ(M=1000000).Set of 5, 200MΩ x 5 all in series... Not cheap!
Arcol Ohmite 13-SERIES CURRENT SENSE AXIAL RESISTORS 5Pcs 3W- 100mΩ Or 200mΩ | eBay
You find them in condensor microphones, such as the AKG C451. The capsule load resistor is 10G for the in-built JFET preamp.I am wondering about what the application of such a resistor would be.
OK, those would be the non-electret capacitor microphones, the electret mics are so very small that a big resistor would not fit.You find them in condensor microphones, such as the AKG C451. The capsule load resistor is 10G for the in-built JFET preamp.
https://gyraf.dk/schematics/AKG_C535EB.GIF
(not a C451, but similar)
They are not difficult to get
https://uk.farnell.com/w/c/passive-...|25gohm|33gohm|47gohm|50gohm&min_max=f1000194
Yes - proper studio microphones, not telephone handset inserts.OK, those would be the non-electret capacitor microphones, the electret mics are so very small that a big resistor would not fit.