Hello, I am quite new to this whole electronics thing. I have a 3 wire pressure gauge, and I need to measure it output signal onto Labjack U3. I have a circuit schematic of how it should look, however I am quite lost on how to start with making it though breadboard.

It is Figure 2 on this link.
https://labjack.com/support/app-notes/measuring-current

Also, the other question I have is do I have to use a shunt resistor for this?

 

Assuming your sensor is a 4-20mA version then you need a shunt as described in your link.
If it is not then you need to provide details of your sensor.

 

Is there any way i can bypass not using a shunt?

My sensor is the DAR type.
http://www.omega.com/pressure/pdf/DPG1000ADA_DPG1000DAR.pdf

 

The sensor provides an output current. The labjack is looking for a voltage input. The shunt is an easy and convenient way of converting the current signal into a voltage signal. It needs only a commonly available resistor. What have you got against using a shunt?

 

Is there any way i can bypass not using a shunt?

My sensor is the DAR type.
http://www.omega.com/pressure/pdf/DPG1000ADA_DPG1000DAR.pdf

A complete circuit must be created so the shunt is required. Power supply, sensor, ground back to power supply.

This circuit is then connected (essentially no current flowing into the rest of the system (kind of like a volt meter).

 

The sensor provides an output current. The labjack is looking for a voltage input. The shunt is an easy and convenient way of converting the current signal into a voltage signal. It needs only a commonly available resistor. What have you got against using a shunt?

I dont have a shunt available

 

It's just a 240Ω resistor - should be easily available everywhere.

 

I dont have a shunt available

Any 220 to 250 ohm resistor should work. Or a pair of 470 in parallel or 4 X 1k in parallel.

 

So right now I have a 12 volt power supply in series with the with the sensor and 2 100 ohm resistors. From the output wires of the sensor, I am getting about 2 volts. however, the voltage drop from each resistor is 4 volts, and so the sensor is only getting about 4 volts. There is also no current output from the sensor. What am I doing wrong? I took a picture of my breadboard circuit.

 

I can't tell from that picture where the wires go so I don't know whether it is connected correctly.
But where the two resistors should be connected together they go into different rows on the breadboard and so would not be connected (unless their wires happen to touch each other).

 

So right now I have a 12 volt power supply in series with the with the sensor and 2 100 ohm resistors. From the output wires of the sensor, I am getting about 2 volts. however, the voltage drop from each resistor is 4 volts, and so the sensor is only getting about 4 volts. There is also no current output from the sensor. What am I doing wrong? I took a picture of my breadboard circuit.

Lable the wires or zoom out so we can see what's what.

 

I can't tell from that picture where the wires go so I don't know whether it is connected correctly.
But where the two resistors should be connected together they go into different rows on the breadboard and so would not be connected (unless their wires happen to touch each other).

Zoom in on the photo, they are ok.

 

Zoom in on the photo, they are ok.

So they are. Should've gone to Specsavers (or are you spared those adverts?).

 

Here is a better picture. So am not sure if am doing this right. The sensor output wires, I have hook up to a mutimeter and its outputting a voltage of 2 volts, but no current. I hook up the output wires to a LABJACK U3 and its reading 2 volts. From the picture, the voltage between each resistor and the sensor is about 4 volts. 12 volts is coming from the power supply.

 

You may want to look at this

http://www.omega.com/manuals/manualpdf/M3363.pdf

Is it just me but does it look like the circuit resembles Fig 1 a two wire setup rather than Fig 2 a three wire setup

Am I suppose to wire those "6-conductor relay wires" onto the breadboard?

 

Is this the right connections?? I am getting a 1.5 volts reading when i connect the (+) probe to the White signal wire and the (-) probe to the Green wire at the end of the Shunt. I have the GREEN signal wire, the GREEN wire at the end of the shunt, and the (-) lead from the sensor all to the ground. I have the 2x100 ohms resistors in series.









I am confused about when you talk about the 3 wire sensor. There is the wire I pointed out in the picture below, is that wire I am suppose to connect to the ground also? Thank you guys for the fast response. It has been really helpful.

 

Here is the schematic of what I believe we have on the breadboard. I am still lost to where the common wire is or located. I was getting a 2.37 mA out of the Output Signal, and I have a reading of 1.53 volts into labjack.

 

Plug power into the red (+) and blue (-) strips on the far side of the breadboard.

Plug the + sensor wire into the red strip of breadboard (far side)

Plug the Vs wire from sensor into red (+) strip of breadboard (far side)

Plug common of sensor into (-) blue strip of breadboard (far side)

Plug one end of a resistor1 into the blue (-) breadboard and the other into the breadboard grid

Plug Resistor2 into same row of breadboard grid as second lead of Resistor1.

Plug second Lead of Resistor2 into an unoccupied row on grid

Plug sensor "signal" + output to unconnected end of Resistor2

Connect AINx to same point as previous (on Resistor2)

Connect SGnd to blue(-) rail on breadboard.

 

Looks about right, from the data sheet I linked, I would interpret the Black & Green wires are connected internally.

The data sheet mentions a test function, have you tried that and recorded your measurements ?

Do the measurements agree with the pressure applied ?

So the "Black & Green" wire are the common wire which is connected internally?
I have not touch to Test function yet.
The pressure gauges are hooked up to a system, which I don't have a pressure to compare it to.

 

Yes, that is how I take it from the data sheet.

I would try the test function.

Now I know i mention that I was getting a reading about 1.5 volts, am I suppose to be getting a current reading also? I tested it and it's not giving me any current.