Motorbhoy Posted January 21, 2010 Share Posted January 21, 2010 Hi, I have a LJ U3 HV. I've recently bought a LJTick-InAmp to connect a couple of K Type Thermocouples. Can anybody point me in the direction of a sample sequence to read values using this setup ? I have other LJ temp. sensors running but am struggling to get this up and running. cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted January 21, 2010 Share Posted January 21, 2010 Just read it using the stand A to D channel type, then apply a conversion to it. The conversion depends on what you have the amplifier set to. If its set to, say 100x, and you want to just use a fixed room temp for CJC, then it'd be: TypeK(value / 100, 22) where 22 is the room temp in degrees C, and 100 is the amplification setting. Link to comment Share on other sites More sharing options...
Motorbhoy Posted January 22, 2010 Author Share Posted January 22, 2010 Hi, Thanks for that. Doing as you've suggested just returns the last number in the conversion :22 My conversion is: typek = value / 201,22 (The gain is set to 201). My Channel is set to A to D any ideas? cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted January 22, 2010 Share Posted January 22, 2010 The conversion is: typek(value/201,22) You should never have a single = in a conversion. Link to comment Share on other sites More sharing options...
Motorbhoy Posted January 25, 2010 Author Share Posted January 25, 2010 Got you. I didn't realise 'Typek' was known. That was the name of my conversion! I'm now getting results of 70. I'm guessing that's not correct either. Link to comment Share on other sites More sharing options...
AzeoTech Posted January 25, 2010 Share Posted January 25, 2010 typeK() is built in a function, like sin() and cos(). If you are getting 70, then probably your amplification is slightly off. You really need to calibrate. There's a big blog article about this: http://www.azeotech.com/board/index.php?&showtopic=3309 Link to comment Share on other sites More sharing options...
BeeHay Posted January 26, 2010 Share Posted January 26, 2010 So there is no extra config to the labjack when using an LJTick-InAmp? We are thinking we need a few of these to convert our differential mode inputs into single ended inputs. Each amplifier converts a differential input to single-ended. Also, are you familiar with the LJTick-DAC? If so, does it require any additional config to get the added analog outputs to function through DF? Thanks! Link to comment Share on other sites More sharing options...
Motorbhoy Posted January 26, 2010 Author Share Posted January 26, 2010 Hi, Thanks for that. I'm that far out I think I have bigger problems than calibration. When I change the gain on the LJ-IA to 51 (Using the dip switches) and change the conversion to: typek(value/51,22) I now get a value flicking between 213 & 214 ?? As the LJ-IA has 2 inputs I changed from A to B, changed the channel number and now get this error: D0050:00:0016 LabJack Device #0 error: Request made on pin not properly configured for analog/digital. I notice my readings don't change during changing input channels. I'm not convinced I'm connected up right. My thermocouple has a green & white wire. I've green connected as '+'ve. Any ideas? cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted January 26, 2010 Share Posted January 26, 2010 Beehay: the tickAmp is a completely external device and so no configuration required on the main labjack unit. You just need to adjust in software for the amplification. I have not use the LJ-tickDAC recently. That does require configuration since there is digital connection between that unit and the labjack. Search this forum or labjacks for the commands to configure it. MB: if the output goes in the opposite direction you'd expect, then the thermocouple almost certainly plugged in backwards. I'd look at the output without a conversion and see if it goes up with heat. Link to comment Share on other sites More sharing options...
Motorbhoy Posted February 4, 2010 Author Share Posted February 4, 2010 Hi There, Me again. The TC is defo. connected correctly now. The voltage increases and decrease the correct way. I think there is something wrong with the conversion. When I set the Gain to 11 and the conversion to: typek(value/11,22) I get a value of 796 (ish). When I set the Gain to 51 and the conversion to: typek(value/51,22) I get a value of 210 (ish). When I set the Gain to 201 and the conversion to: typek(value/201,22) I get a value of 66 (ish). My output offset is always set to 0.4V I'm guessing the mistake here is that the GAIN & Amplification that you refer to aren't the same thing. any ideas? cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted February 4, 2010 Share Posted February 4, 2010 You have to undo whatever gain and offset the labjack and any accessories apply. typek() and all the other thermocouple functions expect the first value to be the raw voltage coming out the thermocouple. If there is an applied offset of 0.4 you need to subtract that out too. Link to comment Share on other sites More sharing options...
Motorbhoy Posted February 5, 2010 Author Share Posted February 5, 2010 Hi, As this voltage and gain is a hardware setting I assume the example bit of code is not suitable for the LJTick-InAmp ? Would I be better off on the LabJack forum for this ? cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted February 6, 2010 Share Posted February 6, 2010 Which example code? The conversion? TypeK(value / 100, 22)? This is a correct example. You just need to back out any amplification and offset. Would I be better off on the LabJack forum for this ? Maybe. I don't know what offset you are referring and if it is in your reading, so can't help you back it out. They should be able to. Bottom line is that TypeK() takes two parameters. The first is the voltage at the thermocouple and should be in the range of about -0.005 to +0.005, which 0.000 being output when the thermocouple is at around the same temperature as the CJC. If you have an amplifier, and an offset being applied by your DAQ hardware, you have to back it out before using this function. The second parameter is the CJC in degrees Celsius. Link to comment Share on other sites More sharing options...
Motorbhoy Posted February 9, 2010 Author Share Posted February 9, 2010 Hi, The Labjack guy sorted me out with an example file: DAQFactory example for LJTick-InAMP In the example the Temperature value is displayed in an expression using your TypeK conversion thus: TypeK((Thermocouple[0]-Offset)/Gain, (InternalTemp[0]-273.15)) Where: Thermocouple - is the channel AIO4 the Thermocouple is connected to. Offset - Is a set value (around 0.4) Gain - is the set gain value (51) InternalTemp - is the U3's internal Temp (Channel 30). I have it working a treat. What's the easiest way to get this into a channel ? cheers MB Link to comment Share on other sites More sharing options...
AzeoTech Posted February 10, 2010 Share Posted February 10, 2010 Replace "Thermocouple[0]" with the word "Value", then put make it a conversion and apply it to the input channel. Link to comment Share on other sites More sharing options...
Motorbhoy Posted February 11, 2010 Author Share Posted February 11, 2010 Thanks for that. Link to comment Share on other sites More sharing options...
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