LM134 Series

7

Figure 3. Centigrade Temperature Sensor

R

226

Ω

LM134-3

134 F03

OUTPUT

10mV/

°C

9.53k

1%

1k

SLOPE

ADJ

10k

ZERO

ADJ

100

Ω

10k

“a”

–15V

LT1009

The two trims shown in Figure 3 are still intended to be a

“one point” temperature calibration, where the zero and

the slope are trimmed at a single temperature. The LT1009

= 25

°C. The 1k trimmer then adjusts the output for 0.25V,

completing the calibration. If the calibration is to be done

at a temperature other than 25

°C , trim the LT1009 for

2.7025—(1

adjust the 1k trimmer for proper output.

If higher accuracy is required, a two point calibration

technique can be used. In Figure 4, separate zero and slope

trims are provided. Residual nonlinearity is now the limi-

tation on accuracy. Nonlinearity of the LM134 in a 100

°C

span is typically less than 0.5

°C. This particular method of

trimming has the advantage that the slope trim does not

interact with the zero trim. Trim procedure is to adjust for

output at some convenient second temperature. No fur-

ther trimming is required.

226

Ω*

≥ 5V

R

LM134-3

134 F04

OUTPUT

10mV/

°C

332k

1%

11k*

1%

SLOPE

TRIM

500k

ZERO

TRIM

10k

15k

50k

–15V

LT1009

*LOW TC, STABLE RESISTOR

Figure 4. Centigrade Temperature Sensor with 2 Point Trim

APPLICATIO S I FOR ATIO

TYPICAL APPLICATIO S

R

LM334

R1

230

Ω

1%

R2

10k

1%

C1

0.1

µF

R3*

600

Ω

134 TA03

*OUTPUT IMPEDANCE OF THE LM134 AT THE “R” PIN IS

APPROXIMATELY

NEGATIVE RESISTANCE CAN BE REDUCED BY A FACTOR OF

5 OR MORE BY INSERTING AN EQUIVALENT RESISTOR IN

SERIES WITH THE OUTPUT.

16

134 TA04

R

LM334

R1*

D1

1N457

R

LM334

134 TA02

Basic 2-Terminal

Current Source

Low Output Impedance

Thermometer (Kelvin Output)

Zero Temperature

Coefficient Current Source