TG Meter - substitution info
I read that a 2.4mA meter is required but is there any chance of using an easy available 1mA sifam meter ?
Yep, easy. Just an adjustable shunt - take about 22r resistor connected in series with 200r multiturn trimpot; than connect them in parallel to your meter.
Feed some voltage thru appropriate variable resistor (for 5V, the 2.4mA current will be at 2.083 Kohm);monitor the current with milliamp meter (Fluke at 20mA range) and adjust the shunt for FSD (full scale deflection, 100%)when the current is exactly 2.4 mA. For this purpose, 2k083 resistor (may bit vary due to total resistance of shunt and meter)
done from 1k5 resistor and 2k potentiometer, connected in-series. Adjust 2.4 ma - adjust FSD - readjust 2.4ma - readjust FSD - done.