It's something simple, and yet I'm having a hard time figuring this out.

I'm trying to build a simple wheatstone bridge resistance finder. This is what I've breadboarded so far, but I'm getting zero current across my ammeter no matter where I leave the rheostat. The resistors are ~100 ohms each (measured by multimeter) and the rheostat starts at zero and is linear taper to 1 Mohm. The voltage is 1.5V DC. I've checked for shorts... I have no idea why this isn't working.

Ideally what I want is for the ammeter to read zero when the rheostat is set to ~100 ohms and to read basically anything else when the rheostat is off and the circuit is "unbalanced." I'm sure I'm missing something stupid.

If I have this calculated correctly (and unlike Tony Stark, my math is often wrong), the current through the ammeter should read as high as 2.5 mA and it's capable of reading in the microamp range.

Thanks for the help in advance.

 

I think I see 150 ohm resistors, but I can't see the wiring well enough.
It's supposed to work like this:

 

I think I see 150 ohm resistors, but I can't see the wiring well enough.
It's supposed to work like this:View attachment 114666

Thanks for the reply. That's pretty much exactly what I have. I diagrammed the circuit I have up there and attached it to this reply.

Could it be a multimeter issue? It's a digital multimeter does seem to respond very slightly when I power down the circuit or move things around... so I'm pretty sure it's functioning (I don't have it handy to test as I type this) and I'm using the unfused inputs so there's no chance a blown fuse could do it. This is the multimeter I'm using, in case it's relevant:

https://www.amazon.com/Extech-EX470-Thermometer-Capacitance-Measurements/dp/B0000WU1A2

(And I got it at way less than it's being sold for there, I didn't pay $100 for it.)

EDIT: Never mind. Close the thread, I'm a moron. I looked up the multimeter manual and I was using it wrong.

 

Yeah, like, you forgot to move the leads to measure current.

 

Thanks for the reply. That's pretty much exactly what I have. I diagrammed the circuit I have up there and attached it to this reply.

Could it be a multimeter issue? It's a digital multimeter does seem to respond very slightly when I power down the circuit or move things around... so I'm pretty sure it's functioning (I don't have it handy to test as I type this) and I'm using the unfused inputs so there's no chance a blown fuse could do it. This is the multimeter I'm using, in case it's relevant:

https://www.amazon.com/Extech-EX470-Thermometer-Capacitance-Measurements/dp/B0000WU1A2

(And I got it at way less than it's being sold for there, I didn't pay $100 for it.)

EDIT: Never mind. Close the thread, I'm a moron. I looked up the multimeter manual and I was using it wrong.

No shame in this. It is called "learning". You can only call yourself a moron if you keep making the same mistake.