|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
99.181.45.74
In Reply to: RE: How to add tube current meter to 300B amp?? posted by SteveBrown on March 20, 2014 at 10:06:55
Yes, the wiper goes to ground. I planned on putting the meter there.
I just need to know how to shunt the meter to make it read 0-100mA.
Follow Ups:
Use a variable voltage source and pass a current so that 1ma flows. Measure the voltage. Internal R = v/i. That R becomes one part of a parallel circuit. You know 1ma across, at a particular V, so then at that V what R do you need to pass the other 99ma. Solve for that (will be a tiny resistance), and there you go.
The easy way to do this is to use a multimeter to measure the resistance of the meter. Shunt resistance should be 1/99th of the meter's resistance.
I thought about that but I didn't know if the voltage of the ohm meter might damage the 1ma meter, I guess not.
Start on a high resistance setting (the current will be very low). Switch to lower scales, watching the meter being measured. Stop before the needle goes off scale. That way you can be sure.
I'll be sling'in solder this weekend. Thx, Al
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: