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TO08 and High COM Ports

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TO08 and High COM Ports

Postby liber » Wed Feb 23, 2011 12:22 am

Hi,

I have a program that supports old legacy serial TC08; we use USB-COM adapters based on FTDI chips. Recently I came across the following issue: if the adapter is assigned COM port numbers below 10, both PicoLog Recorder and my program (which uses tc0832.dll) work fine, but if COM ports are higher than 10, TC08 is not detected - neither in PicoLog, nor through the DLL. At the same time, I noticed that the list of COM ports in PicoLog goes all the way up to 20. If I use another means of communicating with TC08, e.g. something similar to Hyperterminal, I can successfully talk to it on high COM ports too. Now I have two questions:

1) Is the problem with high COM ports a known issue? If yes, is there a workaround?

2) If there is no workaround, I can talk to TC08 through a different program using a protocol described in paragraph 3.4 of the manual, but I need some clarifications:

a) The CJ equation for "result" (from paragraph 3.4) mentions "divisor", but if this equation is correct, the "divisor" is cancelled out, so that the voltage is actually 65535*th/ref. Is that correct?

b) The conversion table of CJ "results" to temperature only goes to 40 degC. Do you have data for temperatures up to 60 degC?

c) If you have any additional documentation on communicating with TC08 and interpreting results without use of tc0832.dll, can you provide it? I am talking about filtering, conversion of voltages to temperature for different thermocouple types, etc.

Thanks!

Sergey Liberman
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Re: TO08 and High COM Ports

Postby ziko » Wed Feb 23, 2011 4:53 pm

Hi thank you for your post.

The COM port does have to be below 10, this is a known issue, the workaround is to change your com port number in device manager to a lower port by going into advanced.

In terms of section 3.4 that has baffled me, it does actually cancel out I agree, I might have an idea why it is there but ignore the divisor so the equation becomes :

Result = (65536 * th)/ref)

The TC-08 should not really be exposed to high temperatures otherwise the readings will not be as accurate and as such there is not point in having the cold junction above 40deg, really should be between 20-30degC.

In terms of the table for k type thermocouples and other thermocouples, this is not a pico specific thing you can find the reference tables for different thermocouples on the web. All the other information is available in the documentation.

Kind regards

Hope this helps.
Ziko

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