Voltage to change batteries

[tauzero]

17 hours ago, Togomi said:

I've already got a TRS jack, but it's not possible to measure the voltage.

0V.

 

Imposible in these basses.

 

Which bass?

[Togomi]

2 hours ago, tauzero said:

 

Which bass?

Fender American Deluxe jazz bass and American Elite Precision bass.

[Woodinblack]

4 minutes ago, Togomi said:

Fender American Deluxe jazz bass and American Elite Precision bass.

 

Yep, they have switched sockets, there is no power on that.

[Dood]

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

[Stub Mandrel]

6 hours ago, Dood said:

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

 

A very high input resistance voltage probe would do the job.

[Woodinblack]

18 minutes ago, Stub Mandrel said:

 

A very high input resistance voltage probe would do the job.

 

Only on a circuit with no reverse voltage protection or anything.

[tauzero]

7 hours ago, Dood said:

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

As I said on page 1, a DVM has a very high impedance and so you'll finish up with a potential divider between the preamp and the DVM. The lower the drain current of the preamp, the higher its effective resistance so the lower the DVM will read for the same battery voltage.

 

24 minutes ago, Woodinblack said:

Only on a circuit with no reverse voltage protection or anything.

 

If it has reverse voltage protection, that would just be a diode, so drops 0.6V as it would be forward biased. And that 0.6V would be lost to the preamp anyway IYSWIM.

[Woodinblack]

27 minutes ago, tauzero said:

If it has reverse voltage protection, that would just be a diode, so drops 0.6V as it would be forward biased. And that 0.6V would be lost to the preamp anyway IYSWIM.

 

Of course it would, but not sure why that is relevant to the battery voltage? You aren't trying to establish the voltage the preamp needs, I assumed people are trying to put a lot of effort into measuring a battery

 

[tauzero]

58 minutes ago, Woodinblack said:

 

Of course it would, but not sure why that is relevant to the battery voltage? You aren't trying to establish the voltage the preamp needs, I assumed people are trying to put a lot of effort into measuring a battery

 

 

No, it's just another inaccuracy in the reading. It does mean that if you have two identical preamps, one with a diode protection and the other without, then the one without will continue working while the battery drops a further 0.6V after the one with the diode has died.