# Conversion part Daq Fctory Express

## Recommended Posts

Hello,

My pressure sensorS will be Same properties.

Pressure sensor 1
Pressure Sensor 2

0...1.6 bar
0 to 20 mA
DC 10 to 30 Volt.

This is Same for both pressor sensor

Now I want to Show the Same value of both pressure sensors in the Daq factory.

But now I am stuck in the conversion part my main is to show both pressure sensors values in the display.

But which kind of formula or expression I used in conversion so that exact values will show on the page.

Thank you

##### Share on other sites

Does the channel currently read a number from 0 to 20?  Or does it read a number from, say, 0 to 5?  As an example, if it reads 0 to 20 and 4 corresponds to 0 bar, and 20 corresponds to 1.6 bar then the Conversion would be:

Value * 1.6 / 20

Basically, when 0 = 0, the math is super simple.  It is just Value * engineering max / raw reading max.

##### Share on other sites

Hello,

Yeah, I understand that thing but for more clarity, I will rectify my query again.

These are my 2 pressure sensors values which are showing in the sensor display:

Pressure Sensor1= P1= 609millibbar = 0.609 bar.

Pressure Sensor2= P2= 610millibar = 0.610 bar.

Now I want to show exact these values on the graph which I made on the page so how I can do this in a simple way because I am getting different values than these values.

Thanks

Kriti.

41 minutes ago, AzeoTech said:

Does the channel currently read a number from 0 to 20?  Or does it read a number from, say, 0 to 5?  As an example, if it reads 0 to 20 and 4 corresponds to 0 bar, and 20 corresponds to 1.6 bar then the Conversion would be:

Value * 1.6 / 20

Basically, when 0 = 0, the math is super simple.  It is just Value * engineering max / raw reading max.

##### Share on other sites

Sorry, but that didn't clear it up.  What is the raw reading when you have 0.609 bar?  The DAQ device you are using is likely not outputting values in engineering units (bar, psi, etc) but more likely as either volts, mA, or in a value from 0 to some full scale value dependent on the DAQ, usually either 4091 or 65535.

##### Share on other sites

The raw reading which is showing in the graph is P1=11.64 Bar and P2 = 11.98 Bar that is totally different from the both pressure sensor readings.

for the unit bar, I clicked the graph properties on the page and change the unit into Bar.

and my main purpose is to show the same values in both pressure sensors as well as in both the graph for this I need the right formula which I have written in the conversion part.

##### Share on other sites

OK, the "unit" setting in graphs and other components are just a label.  They don't actually change the value to that unit.  DAQFactory has no idea what units 11.64 and 11.98 are in.  If you are using a 0-20mA DAQ device than it may be in mA.  You need to figure this out first, or you need to do a two point calibration by taking the reading in DAQFactory and the actual reading in your system at two different pressures, ideally as far apart as possible.  Then you can calculate the slope/intercept to convert between whatever units you are seeing in DAQFactory and pressure.

Note that this is not a DAQFactory thing.  You would have to do this with any software tool as the software has no idea what you have wired into the DAQ and only gets a number from DAQ hardware.

##### Share on other sites

Okay,

as per you said today I took fresh readings of both pressure sensors(P1, P2) as well as also wrote down the values which are showing in the Daq Factory without using any conversion or any formula you can say that these values are the ideal values. In the Table, you can see clearly that in the software reading much different as compared to the pressure sensors readings.

For reference, I also make a small video and send a  reading table so that you can understand more clearly what I want to say that to you and one thing which I cleared that the Daq Factory shows the values only in the voltage or volts so it means that the reading which is shown in my laptop screen is in volts not in Bar.

So in a simple way how can, I convert these values which shown in volts into Bar so that both the same values will be shown in the pressure sensors as well as in the software.

Note: 0-20mA is the pressor sensor current I also add the pic.

Kriti.

##### Share on other sites

OK, so the LabJack is going to give DAQFactory a voltage reading.  It looks like your sensor is, as you said, a 0-1.6 bar with an output range of 4-20mA.  That means that at 0 bar it will likely output 4mA, and at 1.6 bar it will output 20mA.  The problem is that LabJack's don't read mA readings without a resistor to convert it to a voltage, and that conversion factor is determined by which resistor you choose, as defined by Ohms law (V = IR).  So if you used a 250 ohm resistor then 20mA will give you 5V.

When looking at the numbers you provided, I see two things:

1) P2 is pegged at 5V which means that you have a wiring problem, possibly a resistor that is too big.

2) your two point cal is way to close.  682 to 688 isn't much of a span.  You will get a very inaccurate slope doing this.  You should instead choose, say, 682 and 0.

But before you can do the two point cal, you need to address P2 and why it shows 5V.  If both inputs have the same resistor, you should get about the same voltage from both sensors.

##### Share on other sites

Quote

OK, I understand there is a problem with P2 due to resistor as you mentioned. I will check with the resistors and try to rectify it hopefully but my question is that:

Let's say P1 and P2 give the same pattern of values ( i.e. in Volts) than how I will change these values (Voltage) into pressure (bar). Can you give me conversion factor or formulas to change voltage value into pressure value because at last, my main aim is to show the same values in DAQ or in pressure sensors.

Kriti

Okay,

as per you said today I took fresh readings of both pressure sensors(P1, P2) as well as also wrote down the values which are showing in the Daq Factory without using any conversion or any formula you can say that these values are the ideal values. In the Table, you can see clearly that in the software reading much different as compared to the pressure sensors readings.

For reference, I also make a small video and send a  reading table so that you can understand more clearly what I want to say that to you and one thing which I cleared that the Daq Factory shows the values only in the voltage or volts so it means that the reading which is shown in my laptop screen is in volts not in Bar.

So in a simple way how can, I convert these values which shown in volts into Bar so that both the same values will be shown in the pressure sensors as well as in the software.

Note: 0-20mA is the pressor sensor current I also add the pic.

Kriti.

##### Share on other sites

Hello,

As you said last Friday I corrected the P2 and I also wrote the fresh reading.

0.656 Bar                              0.658 Bar

Daq Factory Readings :        1.257V                                   1.264 V

I used 2 point calibration formula and the answer is almost 0.52.   So, in the conversion, I wrote in the formula (Value*0.52).

After that switch on the Vaccum pump the current readings are:

0.709  Bar                             0.710 Bar

Daq Factory Readings :           0.688V                                  0.690V

Still, the values are not similar as you can see those above readings.

Can you please elaborate, what is the next step will I do so that in both the systems the values will be showed the same?

For reference, I also upload the short video.

KRITI

##### Share on other sites

You did the two point cal with two points from different sensors.  That doesn't mean anything.  That is apples and oranges, even though the sensors are the same manufacturer.  You need to do the two point call on each sensor, so for example: P1 at 0.656 and 0.709 bar (1.257 and 0.688V)

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.