Campbell-scientific HMP35C Temperature and RH Sensor Instrukcja Użytkownika Pobierz pdf (Strona 3)

1

MODEL HMP35C

TEMPERATURE AND RELATIVE HUMIDITY PROBE

1. GENERAL DESCRIPTION

The HMP35C Temperature and Relative

Humidity probe contains a thermistor for

measuring temperature and a Vaisala

capacitive polymer H chip for measuring relative

humidity.

The -L option on the model HMP35C

Temperature and Relative Humidity probe

(HMP35C-L) indicates that the cable length is

user specified. This manual refers to the

sensor as the HMP35C.

2. SPECIFICATIONS

Operating Temperature: -35° to +60°C

Storage Temperature: -40° to +80°C

Probe Length: 25.4 cm (10 in.)

Probe Body Diameter: 2.5 cm (1 in.)

Filter: 0.2 µm Teflon membrane

Filter Diameter: 1.9 cm (0.75 in.)

Power Consumption: < 4 mA

Supply Voltage (via CSI switching circuit):

7 to 35 VDC

Settling Time after power is switched on:

0.15 seconds

2.1 TEMPERATURE SENSOR

Sensor: thermistor (100 kΩ @ 25°C)

Temperature Measurement Range:

-35° to +55°C

Thermistor Interchangeability Error:

Typically < ±0.2°C over 0° to +60°C, ±0.4°C

@ -35°C

Polynomial Linearization Error:

< ±0.5°C over -35° to +50°C

2.1.1 Temperature Sensor Accuracy

The overall probe accuracy is a combination of

the thermistor's interchangeability specification,

the precision of the bridge resistors, and the

polynomial error. In a "worst case" all errors

add to an accuracy of ±0.4°C over the range of

-24°C to 48°C and ±0.9°C over the range of

-38° to 53°C. The major error component is the

interchangeability specification of the

thermistor, tabulated in Table 1. For the range

of 0° to 50°C the interchangeability error is

predominantly offset and can be determined

with a single point calibration. Compensation

can then be done with an offset entered in the

measurement instruction. The bridge resistors

are 0.1% tolerance with a 10 ppm temperature

coefficient. Polynomial errors are tabulated in

Table 2 and plotted in Figure 1.

TABLE 1. Thermistor Interchangeability

Temperature

(°C)

Temperature

Tolerance (±°C)

−40

0.40

−30

0.40

−20

0.32

−10

0.25

0 to +50 0.20

TABLE 2. Polynomial Error

Temperature

Range(°C)

Error (°C)

−40 to +56 <±1.0°C

−38 to +53 <±0.5°C

−24 to +48 <±0.1°C

2.2 RELATIVE HUMIDITY SENSOR

Sensor: Vaisala capacitive polymer H chip

Relative Humidity Measurement Range:

0 to 100% non-condensing

RH Output Signal Range:

0.002 to 1 VDC

Accuracy at 20°C

±2% RH (0 to 90% Relative Humidity)

±3% RH (90 to 100% Relative Humidity)

Temperature Dependence of Relative Humidity

Measurement: ±0.04% RH/°C

Typical Long Term Stability:

Better than 1% RH per year

Response Time (at 20°C, 90% response to

steep change in humidity):

15 seconds with membrane filter

1 2 3 4 5 6 7 8 ... 15 16

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