15-12-2020, 08:15 AM
A small point. I don't know if the switched are break before make or otherwise. If they are break before make then you will get momentary open circuit when changing settings. If this will harm your circuit then make sure there's a fixed resistor in parallel with the box. You can check with a meter to see if you get an open circuit when slowly switching between steps.
The greatest errors are likely to be when you get a "carry". So from 999R to 1000R, 99.9k to 100k etc. You can check with a DMM if this is a worry.
Personally, I'm not keen on decade boxes and have found little use for them. This is partly because I've often worked with circuits where the stray L and C from a decade box are unacceptable. I've tended to stick in a pot, adjust on test and measure the result. Often with a series or parallel resistor to get close to the result because this makes the pot easier to adjust and gives less scope for harm. The pot can be anything from a tiny preset (often multiturn) to a hulking great rheostat depending on what I'm doing.
The greatest errors are likely to be when you get a "carry". So from 999R to 1000R, 99.9k to 100k etc. You can check with a DMM if this is a worry.
Personally, I'm not keen on decade boxes and have found little use for them. This is partly because I've often worked with circuits where the stray L and C from a decade box are unacceptable. I've tended to stick in a pot, adjust on test and measure the result. Often with a series or parallel resistor to get close to the result because this makes the pot easier to adjust and gives less scope for harm. The pot can be anything from a tiny preset (often multiturn) to a hulking great rheostat depending on what I'm doing.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
