This circuit from a 1980 publication, converts the temperature sensed by Q1 into a frequency in a linear range of 10Hz / oC from 0 to 100º C. The circuit can be powered by voltages from 18 to 36 V and other silicon transistors can be used as sensors. The operation adjustment is made in PR1 and C1 determines the generated frequency range, which can be changed. Other operacional can be tested in place of the 741.
