AD590: Measuring the current output

Document created by analog-archivist Employee on Feb 23, 2016
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In the Test Center, we have a project on  measuring low temperatures on
Aircraft. In this case, there is a need to measure temperature as low as
-55 deg centigrade. Therefore we're interested in with your AD590
product to get the solutions.

However, we don't have any current sensing equipment. In this condition,
is it possible to use your AD590 product with a voltage sensing
equipment with 1 Mohm input impedance? If it is, please send us the
details by e-mail.

 

The AD590 has a current output of 1uA/K, giving a current output of 218.2uA at
-55 degC to 398.2uA at +125degC. To measure the temperature reading, you need
some way to detect this current. The simplest way is simply to connect the
positive terminal of hte AD590 to the supply voltage, connect the negative
terminal to a resistor of suitable value to convert the current to a voltage in
a range which you can measure conveniently, as shown in figure 4 on page 5 of
the datasheet.  For example a 25k Resistor will give you approximately 10V at
155deg C and 5.45V at -55deg C. You also need to provide the AD590 with power,
in this case a supply voltage of at least 4V. So in the example above, you
would require a supply voltage of >14V (10V over the resistor and 4V min over
the AD590)

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