So what about going the other way. Using a meter rated for a larger current value and getting it into a requirement for a lower current flow. for example a 1 milliamp meter to replace a 60 microamp meter? Thanks Ben...
Thanks! Using nichrome wire is a bad idea ... if you have it. Often the resistor value is quite small, so nichrome wire might be a bit too resistive for this application, depending on the specific resistivity of the wire and the value you are trying to achieve. 🙂
I found a small ammeter and wanted to use in a classic car. I am assuming I have found it’s beyond use in this application providing I have calculated correctly. The gauge shows 120amps full scale. After characterising I have determined it has internal R = 9.1ohm and 13.5mA full scale. Calculations: 13.54v applied. 992ohm Rs (inline resistor). 0.4ohms offset. 991.6+9.1=1000.7 13.54v/1000.7 = 0.01353 = 13.5mA If I wanted to use the fullscale of 120A I would need a 0.0010ohm shunt. If I reduced the scale to 15A I would need a 0.008ohm shunt. Possible? Correct? Love the guides. Many thanks
Thank you! And you are very welcome! 🙂 Good question! Yes, if your characterisation of the meter is correct, then you would need a 0.001024Ohm resistor as a shunt for 120 Amps. Be careful! Your shunt needs to have the current carrying capability for the 120 Amps + proper derating. So, in my book this is 120 x 1.5 = 180 Ams at a very minimum. I suggest using some sheet or bar copper as the shunt. Use a Dremmel tool to whittle away the edges to adjust it to your 0.001 Ohms. Dropping back to a 15 Amp shunt (22.5 Amps for derating purposes), the resistance is now 0.008197 Ohms. Here you could use some #16 copper wire (chassis wiring rated at 22 Amps). This would have to be about 2ft long. Hope this helps. 🙂
Very helpful. I’m converting a 50mA analog Simpson meter to indicate 250 mA. Brilliant. Same scale even. My meter will also have a 10 ma scale for reading a grid current in my application. I get to build two shunts!
good video 😊 To deal with electric measurements is like doctor jokes who visited the doctor which visitet dhe doctor of the doctor of your doctor and who was the ethalon first doctor and how and why he is a doctor and like that is also with voltmeters amperemeters and with all meters that exist bcz bro you cant measure infinite you can get close but whe did you refered that you get that precious value if you understand what im meaning
I wish I had techaers like you in physics and electornics back then. Comprehensive and clear explanation that surely grabs your attention. Thanks!
Wow! Thanks for the great encouragement! 🙂
A great presentation. Comprehensive but clearly explained without dallying for too long in discussion.
Thanks! I am glad it was helpful to you! 🙂
What a great way to begin the day. Notification of a new video from Ralph !
Glad you enjoyed it!
Nice job!
Thanks!
Just printed your formula link. Appreciate you putting that together!
You are very welcome! 🙂
This video was very helpful! New suscriber!
Yay! Thank you and welcome to all the fun!
Excellent!
Glad you liked it! :-)
good work..thanks
You are welcome!
thank you
You are very welcome! 🙂
So what about going the other way. Using a meter rated for a larger current value and getting it into a requirement for a lower current flow. for example a 1 milliamp meter to replace a 60 microamp meter? Thanks Ben...
I'm afraid you'd have to modify the meter itself to do this. 🙂
Ralph, another great video. Your thoughts on using nichrome wire for shunt resistor?
Many thanks & 73.
De K4WRF
Thanks! Using nichrome wire is a bad idea ... if you have it. Often the resistor value is quite small, so nichrome wire might be a bit too resistive for this application, depending on the specific resistivity of the wire and the value you are trying to achieve. 🙂
Thanks for the advice Ralph!
All the best.
Wh
@@watthairston1483 You are very welcome! 🙂
I found a small ammeter and wanted to use in a classic car. I am assuming I have found it’s beyond use in this application providing I have calculated correctly. The gauge shows 120amps full scale. After characterising I have determined it has internal R = 9.1ohm and 13.5mA full scale. Calculations: 13.54v applied. 992ohm Rs (inline resistor). 0.4ohms offset. 991.6+9.1=1000.7
13.54v/1000.7 = 0.01353 = 13.5mA
If I wanted to use the fullscale of 120A I would need a 0.0010ohm shunt. If I reduced the scale to 15A I would need a 0.008ohm shunt. Possible? Correct? Love the guides. Many thanks
Thank you! And you are very welcome! 🙂
Good question! Yes, if your characterisation of the meter is correct, then you would need a 0.001024Ohm resistor as a shunt for 120 Amps. Be careful! Your shunt needs to have the current carrying capability for the 120 Amps + proper derating. So, in my book this is 120 x 1.5 = 180 Ams at a very minimum. I suggest using some sheet or bar copper as the shunt. Use a Dremmel tool to whittle away the edges to adjust it to your 0.001 Ohms.
Dropping back to a 15 Amp shunt (22.5 Amps for derating purposes), the resistance is now 0.008197 Ohms. Here you could use some #16 copper wire (chassis wiring rated at 22 Amps). This would have to be about 2ft long.
Hope this helps. 🙂
Very helpful. I’m converting a 50mA analog Simpson meter to indicate 250 mA. Brilliant. Same scale even. My meter will also have a 10 ma scale for reading a grid current in my application. I get to build two shunts!
Woohoo! Sounds cool! I'm glad to hear my video helped you in building your project. 🙂
Thank you & 73 de YO6OCT!
You are very welcome! 🙂
good video 😊 To deal with electric measurements is like doctor jokes who visited the doctor which visitet dhe doctor of the doctor of your doctor and who was the ethalon first doctor and how and why he is a doctor and like that is also with voltmeters amperemeters and with all meters that exist bcz bro you cant measure infinite you can get close but whe did you refered that you get that precious value if you understand what im meaning
Thanks! 🙂