# Converting Two voltages to through voltage (Solved)

#### Deltafee

Joined May 22, 2015
35
Hello, I have a halleffect sensor which you measure the through voltage between two pins and I want to connect it to raspberry pi which means I need it to be a single analog voltage. When I measure both pins with a grounded voltmeter the V- pin is 4.10V and the V+ pin is 4.11V. Is there some circuit that can measure the through voltage between the two pins and turn it into an analog voltage?

#### MrChips

Joined Oct 2, 2009
26,470
We don't know what you mean by "through voltage".
If you provided the make and model number of your hall effect sensor that would help us to provide you with better answers.

If you mean a differential voltage across two pins, then a simple op-amp circuit wired as a differential amplifier will do the job.

Something like this?

#### Deltafee

Joined May 22, 2015
35
here's the data sheet http://www.mouser.com/ds/2/418/KMY_KMZ_MR174B-769335.pdf, I am using the KMZ20 sensor. According to the datasheet you connect the ground of the voltmeter to V0- pin 3 and the the positive of the voltmeter to V0+ pin 1. I tried connecting it to a differential op amp, where I connected V0- to (-) and V0+ to the (+), is that what you recommend, I was just curious if there was a better way to do it.

#### shteii01

Joined Feb 19, 2010
4,644
I am very confused.

Figure 3 shows:
Pin 1 is +V0
Pin 2 is -VB
Pin 3 is -V0
Pin 4 is +VB

Table on page 4 shows:
Pin 1 is V0+
Pin 2 is V0-
Pin 3 is VCC
Pin 4 is GND

Anyone else see a problem?

#### MrChips

Joined Oct 2, 2009
26,470
What I have shown you in post #2 is a block diagram only.
Here is what a differential amplifier should look like using a typical IC op-amp.

R1 = R3
R2 = R4

Vout = -(Vin1 - Vin2) x R2/R1

#### Deltafee

Joined May 22, 2015
35
I am very confused.

Figure 3 shows:
Pin 1 is +V0
Pin 2 is -VB
Pin 3 is -V0
Pin 4 is +VB

Table on page 4 shows:
Pin 1 is V0+
Pin 2 is V0-
Pin 3 is VCC
Pin 4 is GND

Anyone else see a problem?
Yeah I know XD, I contacted the company and it turns out its a misprint. The correct diagram is Figure 3, I tested it both ways to confirm it was a misprint other than that its a good little sensor.