I recently bought a PicoScope 2203. While playing with it for the first time, I noticed some switching sound coming from inside. Is there a relay internally that produces this noise?
Yes, this noise is caused by the relays that select the input range. The amount of switching depends on the software in use and the input range that is selected. This is part of the normal operation of the scope.
The scopes have relays which switch between the high and low voltage ranges on each channel. When running, the input signal is fed through from one input connector to both channel’s A to D converters in parallel to get twice the bandwidth. Then the other input connector is routed through the same pair of A to D converters and so on in a cycle. At any one time, the unused input connector and pre-amplifier chain is set to the highest voltage (lowest gain) condition to avoid injecting cross-talk onto the live channel. If either channel is set to +/-1V or lower, then the gain relay will cycle continuously. The only way to have two channels in use without the relay noise is to have both set to any voltage greater than +/-1V (+/-2V to +/-20V, they can be different).
The scopes have relays which switch between the high and low voltage ranges on each channel. When running, the input signal is fed through from one input connector to both channel’s A to D converters in parallel to get twice the bandwidth. Then the other input connector is routed through the same pair of A to D converters and so on in a cycle. At any one time, the unused input connector and pre-amplifier chain is set to the highest voltage (lowest gain) condition to avoid injecting cross-talk onto the live channel. If either channel is set to +/-1V or lower, then the gain relay will cycle continuously. The only way to have two channels in use without the relay noise is to have both set to any voltage greater than +/-1V (+/-2V to +/-20V, they can be different).
