multimeter with panel meter

[therooster]

I need to mount a digital panel meter in a small enclosure and use it to monitor the voltage and amperage that a pc board in the enclosure is producing.

The item I am making is a 4-20 0-10 volt power source used to test and check various actuators, sensors etc....

Its basically a small power supply.

Anyhow I am using a switch to switch the output from 0-10v out to 4-20ma out and vice versa.....

I can fiqure out how to monitor the voltage but I get stuck when trying to fiqure a way to monitor the current.

Does anyone have a circuit for a multimeter using a panel meter that will do both volts and amps.

I know there used to be some multimeter on a chip schematics out on the net before but I cant seem to find them now....dont even have a clue as to the chip number.....

If someone could talk me thru this...or point out a schematic somewhere on the net where I can get some general ideas from I would appreciate it.

thanks

 

[0x00x0]

One of these IC's may be what you seek:

https://www.digchip.com/datasheets/parts/datasheet/235/ICL7149CM44.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7139.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7139C.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7139CPL.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7149.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7149C.php
https://www.digchip.com/datasheets/parts/datasheet/235/ICL7149CPL.php

To test current, you need the meter in series with either the - or + wire:

**broken link removed**

 

[Torben]

If you measure the voltage across a known resistance, you can work out the current from Ohm's Law. V = IR so I = V/R.

If you put the current across a well-known small-value shunt resistor you should be able to work out the current. I am not sure how accurate this is at 20mA, though.

How much stuff do you intend to run from a power supply spec'd for 20mA?


Torben

 

[BeeBop]

I need to mount a digital panel meter in a small enclosure and use it to monitor the voltage and amperage that a pc board in the enclosure is producing.

The item I am making is a 4-20 0-10 volt power source used to test and check various actuators, sensors etc....

Its basically a small power supply.

Anyhow I am using a switch to switch the output from 0-10v out to 4-20ma out and vice versa.....

I can fiqure out how to monitor the voltage but I get stuck when trying to fiqure a way to monitor the current.

Does anyone have a circuit for a multimeter using a panel meter that will do both volts and amps.

I know there used to be some multimeter on a chip schematics out on the net before but I cant seem to find them now....dont even have a clue as to the chip number.....

If someone could talk me thru this...or point out a schematic somewhere on the net where I can get some general ideas from I would appreciate it.

thanks

How is it you are using a 4-20 loop, without even googling?
https://www.sensorland.com/HowPage028.html
https://en.wikipedia.org/wiki/Current_loop

at any rate, Torben has the correct answer; measure the voltage across a shunt resistor to get your current. (This is how meters do it anyway.)

Perhaps the chip you were thinking of is the ICL7106 3+1/2 Digit LCD Driver with A/D?