What Did I do Wrong.

[telectrix]

Question for trainees only. No qualified sparks to post answers. .

OK. so some time ago, I picked up a Sangamo Analogue Ammeter A.C/D.C. (manufactured 1963) from a car boot for £2. Been lying around for a bit. Thought I's see how it performed.
So.. 12V PSU +ve to 1 end if a 1.2 ohm 1/2 watt resistor. other end of resistor into teminal on the ammeter othe ammeter terminal connected back to -ve of the PSU. Switched on PSU, the ammeter needle kicked up to 1.5A then back to Zero. what should it have read and why did it do what i described?

So lads/lasses, if any, why do I need to go back to school?

@ Lister. give the younger ones a chance first as i think you'll know the answer.

 

[gazdkw82]

I'm going to stick my neck out here and admit I dont fully understand all the details. Perhaps It would be best for me to draw it out.

However, taking an educated guess I'd say the rsring of the resistor is too high?

 

[James]

Draw out the circuit.
All the info required has been given.
A couple of calculations and all will become clear.

 

[telectrix]

I'm going to stick my neck out here and admit I dont fully understand all the details. Perhaps It would be best for me to draw it out.

However, taking an educated guess I'd say the rsring of the resistor is too high?

think of current and power levels. ohms lawis your friend.

 

[davesparks]

I think the key thing here is the date of manufacture, it must have been calibrated in imperial measurments.

So the problem is clearly going to be that you are using metric volts!

 

[telectrix]

I think the key thing here is the date of manufacture, it must have been calibrated in imperial measurments.

So the problem is clearly going to be that you are using metric volts!

volts are volts, whether imperial or metric. over 50 hurts.