LM363 datasheet(16/22 Pages) NSC

16 / 22 page

Typical Applications (Continued)

Curvature Corrected Platinum RTD Thermometer

TLH5609 – 23

70k and 2k should track to 5 ppm C

Less than 5 ppm C drift

Less than 100 ppm C drift

These resistors should track to 20 ppm C

Equivalent circuit showing lead resistance

This thermometer is capable of 001 C accuracy over b50 Cto

150 C A unique trim arrangement eliminates cumbersome trim inter-

actions so that zero gain and nonlinearity correction can be trimmed in

one oven trip Extra op amps provide full Kelvin sensing on the sensor

without adding drift and offset terms found in other designs A2 is con-

figured as a Howland current pump biasing the sensor with a fixed

current

Resistors R2 R3 R4 and R5 from a bridge driven into balance by A1 In

balance both inputs of A1 are at the same voltage Since R6eR7 A1

draws equal currents from both legs of the bridge Any loading of the

R4R5 leg by the sensor would unbalance the bridge therefore both

bridge taps are given to the sensor open circuit voltage and no current

is drawn

Precision Temperature Controller

TLH5609 – 24

Ultronix 105A wirewound

ThermistoreYellow Springs

44032

Setpoint stabilitye25X10b4 CHr

LM363 Datasheet(PDF) 16 Page - National Semiconductor (TI)