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TC08 and druck pressure transmitter

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TC08 and druck pressure transmitter

Postby kenppy » Mon Dec 03, 2012 10:29 am

I have inherited an incomplete hardware and software set to conduct an experiment. I have managed to set up the thermocouples to capture the temperature points successfully but am stuck as to how to use the druck ptx1400 pressure transmitter to read a low vacuum. The set of bits is not likely to be complete -- can I connect the pt to a spare tc08 terminal ? -- and how do I do this?
thanks
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Re: TC08 and druck pressure transmitter

Postby Martyn » Mon Dec 03, 2012 2:51 pm

You would need the Single Channel Terminal Board that you can see on this page http://www.picotech.com/thermocouple.html
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Re: TC08 and druck pressure transmitter

Postby kenppy » Thu Dec 06, 2012 4:36 pm

DSCF5144a.jpg

thanks, I have the terminal board pin1 to the 4-20/5V and pin2 to COM, and set a tc-08 channel to mV but am getting zero reading that does not seem to alter with pressure. Do I need to calibrate this somehow? As I said before -- I have inherited these transducers as is, and they behave similarly.
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Re: TC08 and druck pressure transmitter

Postby Martyn » Fri Dec 07, 2012 11:03 am

I would expect the output, pin 3, to be connected to the terminal board not the power supply pin.

How are you powering the pressure transducer ?
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Re: TC08 and druck pressure transmitter

Postby kenppy » Mon Dec 10, 2012 8:37 am

Martyn wrote:I would expect the output, pin 3, to be connected to the terminal board not the power supply pin.

I'm using a PTX1400 http://www.cuthbertsonlaird.co.uk/pdf/Druck_PTX1400.pdf
not a PMP1400 http://docs-europe.electrocomponents.co ... 11430a.pdf
and the way I read it is that pin3 is not active on the PMP

Martyn wrote:How are you powering the pressure transducer ?

I assumed that power is supplied through the usb similarly to how thermocouples are driven -- should this be powered differently?

I followed the instructions in the SCTB user'e guide and connected pin2 to COM, pin 1 to 4-20mA and the switch to OFF.
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Re: TC08 and druck pressure transmitter

Postby PeterF » Tue Dec 11, 2012 11:25 am

Hi,
If you are using the PTX1400 sensor which is a two pin, 4-20mA device, then you need the following connections and settings:-
A power supply for the sensor of at least +15V DC & up to +28V DC.
Connect the +Ve output of the PSU to pin 1 of the sensor.
Connect pin 2 of the sensor to the "4-20mA/5V" terminal of the SCTB.
Set the "4-20mA" switch of the SCTB to "ON".
Connect the "COM" terminal of the SCTB to the -Ve terminal of the PSU. That completes the current loop.
The 4-20mA will flow through a load resistor on the adapter board, generating between 9.6mV (@4mA) and 48mV (20mA). To convert these voltages into properly scaled readings, you must use the "Scaling" option in PicoLog. If the output of the sensor is 0% at 4mA & 100% at 20mA, you would set up a look-up table to equate 9.6(mV) to 0(%) & 48(mV) to 100(%).
When in the "TC-08 Measurements" dialog box, click "Edit" for the channel in question.
In the "Edit TC-08 measurement" box, click "Options"
In the "Parameter options" box, tick "Use Parameter Formatting" and set "Units" to "%", "Formatting" to your own preference and then click "Scaling"
In the "Parameter Scaling" box, set "Scaling method" to "Table look-up".
In the blank box, you can now enter pairs of "Raw" & "Scaled" readings. In this case the table looks like:-

9.6 0
48 100
(Note the "Space" between the numbers on each line)
Instead of "%", you can substitute the engineering units of your sensor, if you wish.

If you click on "Help", there is a good explanation of the process.

Please contact again if you have any questions.
Regards,
PeterF.
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Re: TC08 and druck pressure transmitter

Postby kenppy » Thu Dec 13, 2012 4:51 pm

thanks for this Peter
PeterF wrote:If you are using the PTX1400 sensor which is a two pin, 4-20mA device, then you need the following connections and settings:-
A power supply for the sensor of at least +15V DC & up to +28V DC.
Connect the +Ve output of the PSU to pin 1 of the sensor.
Connect pin 2 of the sensor to the "4-20mA/5V" terminal of the SCTB.
Set the "4-20mA" switch of the SCTB to "ON".
Connect the "COM" terminal of the SCTB to the -Ve terminal of the PSU. That completes the current loop.

ok, done this
PeterF wrote:The 4-20mA will flow through a load resistor on the adapter board, generating between 9.6mV (@4mA) and 48mV (20mA). To convert these voltages into properly scaled readings, you must use the "Scaling" option in PicoLog. If the output of the sensor is 0% at 4mA & 100% at 20mA, you would set up a look-up table to equate 9.6(mV) to 0(%) & 48(mV) to 100(%).
When in the "TC-08 Measurements" dialog box, click "Edit" for the channel in question.
In the "Edit TC-08 measurement" box, click "Options"
In the "Parameter options" box, tick "Use Parameter Formatting" and set "Units" to "%", "Formatting" to your own preference and then click "Scaling"
In the "Parameter Scaling" box, set "Scaling method" to "Table look-up".
In the blank box, you can now enter pairs of "Raw" & "Scaled" readings. In this case the table looks like:-
9.6 0
48 100

I assume you mean me to put these figures in? if not -- where do I get this from?

PeterF wrote:
(Note the "Space" between the numbers on each line)
Instead of "%", you can substitute the engineering units of your sensor, if you wish.

I take it that whatever is in the speechmarks, "mbar," is only the name of the dimension
I'm measuring vacuum in mbar expecting the minimum to be 50mbar
using the figures above[table look-up] I got a readout but as the vacuum was applied the figure on the screen did not change. I have several sensors with the same effect.

thanks for your help.
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Re: TC08 and druck pressure transmitter

Postby kenppy » Mon Dec 17, 2012 2:55 pm

Peter, I have gone through this again exactly as you indicated and am still not getting a result. When I picked the channel I left it on thermoK. I later tried this with mv and the only difference it made was to show a negative value. It makes no difference on whether the sensor is or is not plugged into the sensor socket there is a constant reading about 20.
Any ideas, I can't think what else to try?
thanks
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Re: TC08 and druck pressure transmitter

Postby PeterF » Tue Dec 18, 2012 11:50 am

Hi,
Firstly, we need to positively identify the operating pressure range of the sensor. Is it "Relative" or "Absolute" pressure and what is the full scale?
For example:-
Relative pressure sensor would be:-
0 mbar at ambient pressure
-1000 mbar at full vacuum

Absolute pressure sensor would be:-
0 mbar at a full vacuum
+1000 mbar at ambient pressure

I will need to know at what pressure the sensor will output 4mA and at what pressure it will output 20mA.
(I can also find that out if you give me the full sensor part number)
With the sensor information I can give you the full settings for PicoLog.
Regards,
PeterF.
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Re: TC08 and druck pressure transmitter

Postby kenppy » Tue Dec 18, 2012 2:39 pm

PeterF wrote:Firstly, we need to positively identify the operating pressure range of the sensor. Is it "Relative" or "Absolute" pressure and what is the full scale?
For example:-
Relative pressure sensor would be:-
0 mbar at ambient pressure
-1000 mbar at full vacuum
Absolute pressure sensor would be:-
0 mbar at a full vacuum
+1000 mbar at ambient pressure

currently I'm doing a test under a bell jar and I'm expecting to see something like 60mbar, so absolute.
PeterF wrote:I will need to know at what pressure the sensor will output 4mA and at what pressure it will output 20mA.
(I can also find that out if you give me the full sensor part number)
With the sensor information I can give you the full settings for PicoLog.

the numbers of the three sensors are 09H/J25676/1/1, 2 & 3
also on the body S/N 02502/09, 10 & 15 in the same order

thanks
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Re: TC08 and druck pressure transmitter

Postby kenppy » Wed Jan 02, 2013 9:05 am

Peter,

I have spoken to Druck expecting individual callibration sheets but they tell me that the info required is on the unit itself, and it is this:

Range; 2.5 bar a
Output: 4 to 20mA
Supply: 9 to 28Vdc

Can you please let me know how to deal with this?
thanks
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Re: TC08 and druck pressure transmitter

Postby PeterF » Wed Jan 02, 2013 12:36 pm

Hi,
With the new data for the pressure sensors I can amend my previous instructions to suit:-
If you are using the PTX1400 sensor which is a two pin, 4-20mA device, then you need the following connections and settings:-
A power supply for the sensor of at least +15V DC & up to +28V DC.
Connect the +Ve output of the PSU to pin 1 of the sensor.
Connect pin 2 of the sensor to the "4-20mA/5V" terminal of the SCTB.
Set the "4-20mA" switch of the SCTB to "ON".
Connect the "COM" terminal of the SCTB to the -Ve terminal of the PSU. That completes the current loop.
The 4-20mA will flow through a load resistor on the adapter board, generating between 9.6mV (@4mA) and 48mV (20mA). To convert these voltages into properly scaled readings, you must use the "Scaling" option in PicoLog. The output of the sensor is 0 bar at 4mA & 2.5 bar at 20mA, you would set up a look-up table to equate 9.6(mV) to 0(bar) & 48(mV) to 2.5(bar).
When in the "TC-08 Measurements" dialog box, click "Edit" for the channel in question.
In the "Edit TC-08 measurement" box, click "Options"
In the "Parameter options" box, tick "Use Parameter Formatting" and set "Units" to "bar", "Number Display", "Field width" to 3, "Decimal places" to 2 and "Scaling for graphs", "Minimum value" to "0", "Maximum value" to "2.5".
Click on the "Scaling" button.
In the "Parameter Scaling" box, set "Scaling method" to "Table look-up".
In the blank box, you can now enter pairs of "Raw" & "Scaled" readings. In this case the table looks like:-

9.6 0
48 2.5
(Note the "Space" between the numbers on each line)

If you click on "Help", there is a good explanation of the process.

Please contact again if you have any questions.
Regards,
PeterF.
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Re: TC08 and druck pressure transmitter

Postby kenppy » Wed Jan 02, 2013 4:01 pm

Peter,
Thanks for that comprehensice reply -- but there is still a problem. I have checked the supply and the connections and switched on, it reads 0.48 ( I was expecting 1.0), now pressurising or pulling a vacuum does not nudge this figure. Everything here is tried on three units with the same results. And now the weird thing is that when I pull the SCTB from the logger the reading is still 0.5 ( is this some kind of default value?) If I restart the run with the SCTB out the 0.5 figure is shown. The only thing that's different to what you say is that the power supply is a max of 21V -- is this significant?

What is going on here?

Thanks
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Re: TC08 and druck pressure transmitter

Postby PeterF » Mon Jan 14, 2013 9:46 am

Hi,
Your supply voltage of 21 volts is fine.
You need to check the wiring of your pressure sensors and SCTB. Unplug the SCTB from the TC-08. Power the sensors and, using a digital voltmeter, check the voltage present at the input screw terminals of the SCTB, where the two wires connect. At 0 bar absolute, the sensor should be allowing 4mA to flow through the 240 ohm resistor on the SCTB and a voltage of 960mV should be measured at the input terminals (4mA & 240 ohms = 960mV). A voltage of 9.6mV should be present on the two output pins of the SCTB which plug in to the TC-08 (100:1 attenuator).
At 1.0 bar absolute, the sensor should be allowing 10.4mA to flow through the 240 ohm resistor on the SCTB and a voltage of 2.496V should be measured at the input terminals (10.4mA & 240 ohms = 2.496V). A voltage of 24.96mV should be present on the two output pins of the SCTB which plug in to the TC-08 (100:1 attenuator).
At 2.5 bar absolute, the sensor should be allowing 20mA to flow through the 240 ohm resistor on the SCTB and a voltage of 4.8V should be measured at the input terminals (20mA & 240 ohms = 4.8V). A voltage of 48mV should be present on the two output pins of the SCTB which plug in to the TC-08 (100:1 attenuator).
Please make sure these voltages are being obtained as otherwise there is no point in attaching to the TC-08.
Let me know how you get on with these measurements, then we can sort the rest out.
Regards,
PeterF.
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