how to connect AD595 thermocouple amplifier?

[jex]

oh..can use the old thread? i thought it will deleted after several days....sorry, i am newbie on forum, at room temperature it only show 5.4mV when i measure using multimeter and my value will be out cause i using normal wire to connect because i will do my own calibrayion later on

[jex]

i found some information regarding the AD595 thermocouple amplifier and i realise that it can meassure the ambient temperature straight away, but i only got 5.4mV when the power supply is on and multimeter is meassure from pin 8 and pin 7, below is my connection where the purpule wire is input and ground of my power supply and yellow and white wire is the place where i put the multimeter, is the circut got problem ? I use normal wire to connect my thermocouple, the range will out so many ??? Can anyone guide me how to connect ?

[LabViewGuruWannabe]

Howdy,

I use these all the time for quick and easy temp measurements. If you want to measure negative temperatures, you will need two batteries or power supplies. (one for + voltage and one for - voltage.) If you don't need to measure negative temperatures, then a single 9V battery works great. Follow the suggested wiring diagrams in the documentation from Analog Devices, and it should work fine. Your thermocouple connects to pins 1 and 14, and the output pins are pin 8 and any of the commons (pins 1, 4 or 13). Seems like you're just measuring one pin wrong.

I use a simple USB analog input device when reading the temp into the comptuer, and do a little math to convert the mV input to degreesC or degreesF. If the output voltage doesn't look right (for example, if the output voltage decreases when the temperature increases) try swapping the thermocouple inputs. The attached schematic is what I use, and it works great (within +/- 1degreeC  accuracy) between different chips or TC's. Attached is a pic of the schematic I use.

B-)

[jex]

what u mean by seems connect 1 pin wrong ? is it pin number 7? i din supply negative voltage so it suppose to grounded rite as my connection shown ? i use multimeter to meassure pin number 7 and 8 rite ? yor schemetic the pin 8 u connect is a device ?

[LabViewGuruWannabe]

I didn't say Pin 1 was wrong, I said you may have connected one pin wrong... Pin 7 is your negative voltage input, so if you're using dual voltage, you want to measure between Pin 8 and Common. If you are using a single voltage, then yes, Pin 7 is Common also. I have Pin 8 connected to an Analog Input channel, or a multimeter.

B-)

[jex]

which means pin 4 is the grounded point ? i just use single supply which means my connection will be pin 7 and 13 connect to pin 4 as comman? then pin 1 and 14 is my thermocouple terminal, pin 8 and pin 4 meassure using DMM, am i correct ?

[jex]

what is yor value shown when u straight away meassure from the DMM, i already according to yor schemetic, and again only when i press the tip, only it can shown the value, if not only 5.4mV, may i know what is the happen actually ? my thermocouple got problem ??

[LabViewGuruWannabe]

At room temperature my meter displays about 0.24-0.26V, and my software muliplies that times 100 to get 25 degreesC. If I stick the thermocouple in the oven, it reads more than 2.10V, or 210 degreesC. I've noticed that if the thermocouple is connected backwards, it outputs a constant voltage, so if you are still having trouble, try switching the inputs at pins 1 and 14.

What type of thermocouple are you using? I believe the AD595 is preset for K-Type thermocouples. If you are using something else, you may have to modify your circuit, or use a different chip.

B-)

[jex]

ya..i am using thermocouple K type that is y i unable to get the value, i wonder is it my thermocouple got problem or not, cause according the schemetic, i only get 5.4mV which means it doesn't have input value at all if the schemetic is correct, the data sheet below is the thermocouple that i use, this type straight away will giv me voltage rite ? i am using PTFE insulated type

[LabViewGuruWannabe]

K-type is correct for the AD595. Have you tried removing the thermocouple from the plug and connecting it directly to pins 1 and 14? If the wiring is correct, you either have a bad thermocouple, or a bad AD595 chip.

Good luck,

B-)