December 2019 108 LDC-3706 Series Laser Controller
Figure A.1 – Non Linearity Graph
If a maximum absolute error of 0.8°C is tolerable (over the entire temperature range), the one
point calibration of C
1
should be used. If C
1
is calibrated at 25°C, and the intended operating
range is 0 to 50°C, a maximum error of about ±0.2°C may be expected over that operating
range. If a greater accuracy is desired, the two point method of determining C
1
and C
2
should be
used. Note however, the absolute error curve is non-linear; therefore, the constant C
2
will vary
over different temperature ranges.
LM335 Sensor
The LM335 is a linear thermal sensor which acts as a constant voltage regulator. It produces a
voltage, V, which is directly proportional to absolute temperature, over its useful range (-40°C to
+100°C). This nominal value can be expressed as:
=10
Where V is the nominal voltage produced by the LM335 and K is the temperature in Kelvin.
The LDC-3706 instruments use V to determine the nominal temperature, T
n
, by the formula:
=
10
−273.15
Where T
n
is measured in °C.
The temperature, T
d
, which is displayed by the LDC-3706, is first calibrated as follows:
=
+
10
∗
Where C
1
and C
2
are the constants stored by the user in the LDC-3706 for the LM335.
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