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Josip
24-03-2013, 05:24 PM
Problem:

Compressor is equipped with UNISAB II where are connected all pressure and temperature probes with output signal in mA (4-20) except two probes for Vi and Capacity with output signal in volts (0-12V) which is not recognized by UNISAB II.

Originally compressor has a Gram-Matic 2502 replaced with UNISAB II (because Gram-Matic PLC is not in production for many years), but we cannot connect Vi and Capacity probe due to mismatch of output signals... what to do now ...

Q:

1. Is it possible to order original probes (Vi & Capacity) for this type of compressor with output signal in mA for direct connection to UNISAB II....

2. Is it possible to use signal converter to convert voltage signal into mA signal ...

3. Some other solution to above problem....


Thanks for your input.

Best regards, Josip :)

Peter_1
25-03-2013, 06:23 AM
This is something which excists right of the shelves Josip. How about this http://www.analog.com/static/imported-files/data_sheets/1B22.pdf.
We often buy at Farnell whom can deliver the next day http://be.farnell.com/crouzet/88-950-108/converter-0-20ma-to-0-10vdc-4-i/dp/1299248 But I don't think to where you are for the moment ;-)
Or you could add a resistor to your circuit and feed that to your controls. But problem will be to find the right high precission resistor. And also the difficulty that you need 4 mA zero at 0 Volt which is impossible.
What's the thread on your probes Josip? Can't you use any probe with the proper signal?

Josip
25-03-2013, 06:08 PM
Hi, Peter_1 :)



This is something which excists right of the shelves Josip. How about this http://www.analog.com/static/imported-files/data_sheets/1B22.pdf.
We often buy at Farnell whom can deliver the next day http://be.farnell.com/crouzet/88-950-108/converter-0-20ma-to-0-10vdc-4-i/dp/1299248 But I don't think to where you are for the moment ;-)
Or you could add a resistor to your circuit and feed that to your controls. But problem will be to find the right high precission resistor. And also the difficulty that you need 4 mA zero at 0 Volt which is impossible.
What's the thread on your probes Josip? Can't you use any probe with the proper signal?


Thanks for advices ... as I'm not an electrical engineer I'm not sure can we use converters from your links .... the same is with precision resistor .... that I have to discuss with electrical engineer here on site. Yes, you are right, here could be a lot of things unavailable of the shelves.

Those probes are very special with movable internal piston and cannot be replace with any other probes. Piston is touching a cone shape on the slide valves for volume i.e. capacity thus moving in and out changing output signal and giving info to Unisab II about Vi and capacity in that moment.

Hope to get some help from Grizzly. Gram GSV 84 compressors are out of production now and retrofitting Unisab II to it is very rare. For that reason I believe there must be replacement probe to fit Unisab II or we have to find solution as per your suggestion.

Best regards, Josip :)

Grizzly
25-03-2013, 10:27 PM
Hi Josip.
I came to the same conclusion as Peter.
I did look at my ancient database but I did not seem to get any further.
I can dig deeper for you, but it will not be for a few days as I am snowed under (With work and commitments at present) Not the weather that many are experiencing.

Cheers Grizzly.

HVACRsaurus
26-03-2013, 03:13 AM
Hi Josip.

Frick Part # 534C1552H01 is a milliamp type encapsulated linear variable distance transmitter. It is a retrofit for the original style axial resistance potentiometer for the larger compressor VI indication, on the smaller Frick XJF's this item is used as the Slide Valve position indicator.

As for the large compressor rotary potentiometer / slide valve indicator you will likely need a converter - I will check details of one that we are using next time I'm on site.

Grizzly
26-03-2013, 06:52 AM
H.
I would give you rep points for your helpful advise. Only I had done on your other post.
So thanks for helping is all I can give this time.
grizzly

Josip
26-03-2013, 08:06 AM
Hi, dear friends many thanks to all of you for valuable inputs.

10161

Here on the photo we can see capacity probe on the left side and Vi probe on the right side. Those are with output signal in volts.

I need the same types, but with output signal 0-20 mA.

Best regards, Josip :)

HVACRsaurus
26-03-2013, 09:01 AM
Hi Josip,

The devices shown in your photo look exactly like the milliamp position transmitter that I am familiar with. I am puzzled as to why anyone would manufacture such a similar transmitter, especially one with such an un-conventional instrument signal (0-12V).

Could your devices actually be the milliamp transmitters that I'm referring to?

Else, 12VDC pushing against 600 ohms resistance creates 20mA (with corresponding changes in milliamps proportional to Voltage), surely some modification of the instrument could be made?

sgull
21-04-2013, 10:12 AM
Hi Josip
Sorry for not noticing this topic sooner.
The voltage output transmitter was used for the Frick Quantum panel (Gram GM2502).
If you change to Unisab 2 you must use the older transmitters.
These are a direct replacement and you can change the electrical part only by loosening the 2 x 3mm allen screws at the side of the transmitter (no need to empty the compressor)
The parts are as follows.
Capacity transmitter 4-20ma 52-021-0603
Volume transmitter 4-20ma 52-021-0604
Both available from Johnson controls
Check wiring before fitting as old wiring would be different (pin 1= +24vdc, Pin 2 = 0vdv, Pin 3 = 4-20ma)
Regards
Denis

Josip
27-04-2013, 09:24 PM
Hi, sgull :)


Hi Josip
Sorry for not noticing this topic sooner.
The voltage output transmitter was used for the Frick Quantum panel (Gram GM2502).
If you change to Unisab 2 you must use the older transmitters.
These are a direct replacement and you can change the electrical part only by loosening the 2 x 3mm allen screws at the side of the transmitter (no need to empty the compressor)
The parts are as follows.
Capacity transmitter 4-20ma 52-021-0603
Volume transmitter 4-20ma 52-021-0604
Both available from Johnson controls
Check wiring before fitting as old wiring would be different (pin 1= +24vdc, Pin 2 = 0vdv, Pin 3 = 4-20ma)
Regards
Denis

Thanks for help ;) ... very useful code numbers to order new transmitters.

Seems 52-021-0604 is replaced with new model 52-021-0608. Just check with refparts...



Best regards, Josip :)