Help me clear some doubts about the usage of XTR105

hello,anyone. recently, i am working with the temperature sensor PT100. the temp range is 0-100 degrees celsius. and i want the output is 4-20mA. and i find that the XTR105 is a good selection for my project. i know how to calculate the value of the resistor. the datasheet has given me a lot of equation. but still i have some questions:

1: the word from the XTR105 datasheet "the XTR105 is available in DIP-14 and SO-14 surface-mount packages and is specified for the -40 degrees celsuis to +85 industrial temperature range", and i donnt understand the word clearly. and my understanding is that: the measure temperature range of PT100 is just -40 to + 85, but what i want to measure is 0-100, the desired temperature range(0-100) is beyond of the datasheeet temperature range(-45 to +85). i donnt know whether i am right.



2: From the datasheet, the IC output is 4-20 mA. that's to say, in the minimum temperature ,the output is 4mA, in the maximum temperature ,the output is 20 mA. but it doesn't

give the resolution. my mean is that: if the temperature is 50.1 degrees celsuis, what the XTR105 will output ?

i donnt konw whether you understand what i mean. looking forward to your reply.

thanks.

Re: PT100 and XTR105

-40 - +85 is the range of XTR105, not PT100 ..
The PT100 has to be located some distance away from the XTR105 ..

From Table.1, for the range of 0°C-100°C the values of resistors should be as follows:
R[Z]=100Ω
R[G]=78.7Ω
R[Lin1]=33200Ω
R[Lin2]=35700Ω

With this in mind, the output current for 50.1°C should be somewhere close to 12.016mA ..

Rgds,
IanP

Re: PT100 and XTR105

IanP said:

-40 - +85 is the range of XTR105, not PT100 ..
The PT100 has to be located some distance away from the XTR105 ..

From Table.1, for the range of 0°C-100°C the values of resistors should be as follows:
R[Z]=100Ω
R[G]=78.7Ω
R[Lin1]=33200Ω
R[Lin2]=35700Ω

With this in mind, the output current for 50.1°C should be somewhere close to 12.016mA ..

Rgds,
IanP

Click to expand...

thanks very much. the first problem has been solven out according to your reply.but the word "the output current for 50.1°C should be somewhere close to 12.016mA .." i just wonder how you get it(12.016ma)? from a formula, or other thing. looking forward to your reply.

Re: PT100 and XTR105

Let’s do some rough calculations without calculator (or computer) ..

From 4mA to 16mA there is 16mA span, and that’s the equivalent to 0-100 range ..

In other words, 0.1degC is responsible for 0.016mA ..
Now, 50degC is the half of the range, that is 4mA (for 0) + 8mA(for 50) => 12mA
So, 50.1degC :arrow: 12mA + 0.016mA

Rgds,
IanP

Re: PT100 and XTR105

IanP said:

Let’s do some rough calculations without calculator (or computer) ..

From 4mA to 16mA there is 16mA span, and that’s the equivalent to 0-100 range ..

In other words, 0.1degC is responsible for 0.016mA ..
Now, 50degC is the half of the range, that is 4mA (for 0) + 8mA(for 50) => 12mA
So, 50.1degC :arrow: 12mA + 0.016mA

Rgds,
IanP

Click to expand...

theoretically, you are quite rught. but i just wonder whether the realistic IC operate in that way, cause i doont find anything about this part in the IC datasheet. what do you think?

Re: PT100 and XTR105

The XTR-ICs are pretty accurate devices ..
If you set them up properly you will have the expected results, have no doubts about that :!:

Rgds,
IanP

Re: PT100 and XTR105

IanP said:

The XTR-ICs are pretty accurate devices ..
If you set them up properly you will have the expected results, have no doubts about that :!:

Rgds,
IanP

Click to expand...

really thank you. i konw what to do now.