SECTION 9. INPUT/OUTPUT INSTRUCTIONS

Thermistor Probe, makes a fast, single-ended voltage measurement across a resistor in series with the thermistor, and calculates the temperature in °C with a polynomial. A 1 before the excitation channel number (1X) causes the channel to be incremented with each repetition. The maximum polynomial error from -40°C to +56°C is given here:

Curve Fit Error --

 

Range (°C)Error (°C)

-40 to +56

+1.0

-24 to +48

+0.1

PARAM.

DATA

 

NUMBER

TYPE

DESCRIPTION

01:

2

Repetitions

02:

2

Single-ended channel

 

 

number of first

 

 

measurement

03:

2

Excitation channel

 

 

number

04:

4

Input location for first

 

 

measurement

05:

FP

Multiplier

06:

FP

Offset

Input locations altered: 1 for each thermistor channel

*** 12 207 RELATIVE HUMIDITY PROBE ***

FUNCTION

This instruction applies a 1.5 VAC excitation across Campbell Scientific's Model 207 Temperature and RH Probe, makes a fast single-ended measurement across a series resistor, calculates the result with a 5th order polynomial, and performs the required temperature compensation before outputting the result in % RH.

When measuring several probes, all the RH elements should be connected sequentially. The temperature values used to correct the RH measurements should also be stored sequentially to make use of the REP feature in Instruction 11.

NOTE: The temperature value used in compensating the RH value (Parameter 5) must be obtained (see Instruction 11) prior to executing Instruction 12 and must be in Celsius.

9-6

The RH results are placed sequentially into the input locations beginning with the first RH value.

In the 207 probe, the RH and temperature elements use a common excitation line.

CAUTION: Never excite the 207 probe with DC excitation because the RH chip will be damaged.

A 1 before the excitation channel number (1X) causes the channel to be incremented with each repetition.

The maximum RH polynomial error is given here:

Curve Fit Error --

 

Range (%RH)Error (%RH)

10 - 100

+4

15 - 94

+1

PARAM.

DATA

 

NUMBER

TYPE

DESCRIPTION

01:

2

Repetitions

02:

2

First single-ended

 

 

channel for RH

 

 

measurement

03:

2

Excitation channel

 

 

number

04:

4

Input location for first

 

 

compensating

 

 

temperature

 

 

measurement (°C)

05:

4

Input location for first

 

 

R.H. measurement

06:

FP

Multiplier

07:

FP

Offset

Input locations altered: 1 for each RH measurement

*** 13 THERMOCOUPLE TEMPERATURE,

***

SINGLE-ENDED

FUNCTION

This instruction uses the selected thermocouple calibration to calculate the thermocouple output voltage at the reference temperature, then it makes a SINGLE-ENDED VOLTAGE MEASUREMENT (Section 13.2) on the thermocouple and adds the measured voltage