Arroyo Instruments TECSource 5400 Series, Руководство пользователя

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5400 Series TECSource User’s Manual · Page 37
Working With AD590s and LM335s
Unlike thermistors and RTDs, an AD590 or LM335 is considered an “IC” sensor
because it has an active transistor element that responds to changes in
temperature by producing a current (AD590) or voltage (LM335).
Also unlike thermistors and RTDs, these IC sensors produce a linear response,
making conversion to temperature a very straightforward calculation.
AD590 sensors produce 1 μ A/K, so that 0°C (which is equal to 273.15K) would
produce 273.15 μ A.
Similarly, LM335 sensors produce 10mV/K, so that 0°C would produce 2.7315V.
For both sensors, because the response is linear, the sensor coefficients default
to a slope of 1 and an offset of zero, but can be adjusted to achieve higher
accuracy.
The temperature correction formula for the AD590 or LM335 is:
T = MT
C
+ B
Where T
C
is the temperature (in °C) calculated using the standard conversion
value of 1°C/ μ A or 0.1°C/mV, as appropriate, and adjusted from Kelvin to
Celsius.
LM335 is only supported by sensor input 1, while AD590 is only supported by
sensor input 3.
Gain Control and the PID Loop
The
TECSource supports a fully configurable PID loop, allowing full
customization of the PID control parameters. To simplify control, eight standard
gain settings are also defined, and many applications can achieve acceptable
performance with these predefined gain settings, eliminating the need to
understand and adjust the PID loop.
The predefined gains are numbered
1 through 300 , and set using the Gain
menu setting. Increasing the gain value will increase the speed of the control
loop. For full access to the PID parameters, change the
Gain setting to PID , and
the individual P, I, and D values will be available as settings in the menu.
The PID parameters function within a mathematical formula as described below: