Is this the right DAQ board to buy?

[hrh1818]

Jimmy, the key thing you need to determine is can an external program send a
request for a temperature  reading  to your  pyrometer and then have the pyrometer
retun the current reading?   Please ask Ircon this question. The answer to this question
would be very helpful in selecting the right data acuisition and control components.

Howard
 

[Jimykid86]

hello howard,

I will ask them that.  Thanks.

Jim

[hrh1818]

Jimmy,

We have gotten off on the wrong track on using the digital output of the Ultimax UX-20P
to control the temperature of a specimen.  You should instead be usnig the analog output
of the Ultimax-20P.  If you use the analog output of the pyrometer the main components you
need to buy then, assuming you already own Labview, are a multifunction DAC board, an
analog isolator and a dc power supply.  

The multifunction DAC board is used to both digitize the pyrometer's analog output signal
and to supply an analog signal to set the SM7020's current.  The manufacturer of the SM7020
says you need to use an analog isolator between the ouput of the DAC board  and the input to
the SM70290.  However, the analog isol;ator does need to be super accurate.  You could even
even build an optical isolator that will do the job.  The dc power supply is used to supply power
to the analog isolator.

Howard

[Jimykid86]

Hello,

I thought the other plan was good.  Is there anything wrong w/ that plan?  I can't find any introductory information on the analog optical isolator.

Jim

[hrh1818]

Jimmy

The major reason for using the analog output of the pyrometer for controlling the temperature of your specimen in place of the RS-232 digital output is we don't know if the RS-232 digital signal is suitable for the task. Secondary reasons are:  One, When you digitize the analog signal with a multifunction DAQ the response time is better and the performance is a lot more predictable when compared with using an RS-232 signal.  Even if you could send a request for a current temperature reading to the pyrometer and receive a reply you don't know how long you have to wait for a reply.  I haven't seen any specification for the amount of time within which the pyrometer guarantees to return a reply. Two, Compared with the RS-232 approach the design of the Labview controller for this task is a lot easier and more straight forward.

As far as I can tell the lowest cost National Instrument product that can produce an analog output signal for setting the SM7020 power supply current are multifunction DAQ boards. Hence if you use the RS-232 approach you will need to buy a multifunction DAQ board. But once you by a multifunction DAQ board why not go all the way and use the analog to digital conversion capability built into a multifunction DAQ board and digitize the pyrometer's analog output signal.  In other words there is no increase in cost when you digitize the a pyrometer's analog output signal. The cost of a multifunction DAQ boards is proportional to the analog to digital conversion rate of the board. National Instruments sells low speed analog to digital conversion boards, which are more than adequate for your task, for under $500.   

Here is an introduction to analog optical isolators.
http://en.wikipedia.org/wiki/Opto-isolator

Howard

[Jimykid86]

Hello Howard,

Thank for the suggestion.  I just look for some DAQ board, and I find this: NI USB-6008.  It has several analog inputs/outputs.  I will probably need to buy an analog cable from IRCON for the handheld thermometer (2.5 mm microphone jack with alligator clips).  The alligator clips end will go on the USB-6008, right?  As for the optical-isolator, I probably don't have time to learn to build one.  I think I will just use a the PSC-232 controller from delta-electronika, and connect it to the computer through the RS-232 port on the computer.  Is the set-up sound right?

Thanks,
Jimmy

[Dennis_Knutson]

Before you go buying a DAQ device, check the manual and with the vendor about the RS-232 interface. The analog out may not be the best option and the output over the RS-232 could be all that you need. It think it would be simpler to set up. If you have a slightly noisy signal connection between the instrument and the DAQ board, you will have to take multiple readings and get an average and the response time will be about the same as a serial connection.

[hrh1818]

Jimmy

I admit I got confused by your first message and I can see why most everybody else got confused. In your first message you implied the DB-15 connector on the back of the power supply was an RS-232 interface.  But any body who looked at the PDF for the SM7020 saw that it wasn't and thought you were on the wrong track.  Then latter on when you mentioned a PSC-232 I completely missed what you meant.  Any how your PSC-232 approach you mentioned a few posts back is looking a lot better now.

You have two valid approaches for interfacing Labview to your SM7020 power supply.  

1.  An RS-232 approach

PSC-232 RS-323 interface to Delta Elektronika SM7020 Power Supply See:     
http://www.delta-elektronika.nl/PSC-232.htm
Digital Cable, 2 m (6 ft.) long, 2.5mm micro phone plug x D-SUB 9-pin connector for Ircon Ultimax UX 20P Pyrometer,  All Ultimax plus Models feature:  RS-232-C digital output.
If you don't have sufficient RS-232 ports on your computer http://www.usbserial.com/465.html sells a dual RS-232 USB converter for $40 or Delta Elektronika tested the UC-232A from ATEN, see www.aten.com

2. A Multifunction DAQ approach

NI USB-6008 Multifunction DAQ      $159
ETISO-V - Analog Isolation Module See: http://www.elkor.net/etiso.htm     $120
24 VDC power supply for the analog isolator   $50         
Ircon accessory Analog Cable, 2 m (6 ft.) long, 2.5mm micro phone plug x alligator clips

Two unknowns keep me from favoring one approach over the other.  One incomplete information on the Ircon Ultimax pyrometer's-232 interface and two the cost of the PSC-232 RS-232 power supply interface compared with the cost of a multifunction DAQ, an analog isolator and a DC power supply.

Howard

[Jimykid86]

Hello Howard,

I just ask delta about the cost of the controller and it is 395 euro or approximately 610 dollars, which is very expensive in my opinion.  What is the missing informaiton of the IRCON thermometer that you need?  I will ask them for you if you tell me.  Anyway, thanks for finding the optical isolator for me.  I don't know that much about eletrical stuff to build it.  Also, I ask IRCON  about th eprice of the digital cable and it is $100.  I think the analog cable is probalby at the same price.  Nonetheless, I think I will go w/ the mulifunction DAQ approach.

Jimmy

[hrh1818]

Jimmy,


My Ultimax UX-20P RS-232 digital interface unknown is can you send a request for the current reading to the pyrometer and is the current reading guaranteed to be return within 0.5 seconds.  The 0.5 seconds number is based on your present mode of operation.  That is you are able to satisfactorily control the temperature of your specimen manually.  Which means you have a fairly large specimen and the temperature does not change rapidly when the power input to the specimen changes.

Action Instruments has an analog isolator, Model AP4380-2000, see http://www.actionio.com/products/actionpak/signalcond/ap4380-2000.html
The advantage of this unit is it does not require a DC power supply.  It uses the 120 AC power line for power.  However, I have not yet received a cost estimate from Action Instruments  You might want to give then a try.  They along with Eurotherm have a reputation for low prices.

Howard