I have an Omega OS102 ir thermometer that I am using in a project to record temps continuously. My data logger has 0-5 volt inputs at 12 bit resolution.
The Omega unit has an analog output of 1 mv per degree C. I am doing all my recording in the 5-37 degree C range, and it would be very useful if I was recording 10mv per degree instead of 1mv.
Is there a way to do this conversion with a simple op amp? What's the best approach to this?
A simple follower-with-gain curcuit will do what you want.
formatting link
The National Semiconductor LF353 is probably not the amplifier you'd want to use
formatting link
since the input offset voltage is typically around 5mV with a worst case of 13mV over temperature, and it would require positive and negative voltage supplies in your application.
I'd be more inclined to use the LT1006
formatting link
,P1211,D1414
which is a single supply op amp with a 50uV input offest specification.
In principle you could probably use a gain of 100 in your application, but you might need to do some heavy low-pass filtering if you did want to run with that kind of gain.
You can build a Sallen and Keyes low pass filter around a single follower with gain, but few text-books analyse the circuit operation at high gain.
formatting link
The two amplifier version of the circuit - as discussed in Williams and Taylor's "Electronic Filter Design Handbook"
formatting link
715-ElecFilter_FM.pdf
- allows you to choose more or less arbitrary values for the two capacitors involved, which makes the design a lot more practicable. E- mail me - my e-mail address is real - if you want more detail. The dual version of the LT1006 - the LT1013 - would work in such a circuit.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.