Product specifications

DS7817 (Rev. E, 1/4/07)
4-1
Perception and Wizard Sensors
7817
External Temperature Sensor
The External Temperature Sensor is used to measure
temperatures in general conditions. It is well-suited for air,
water, or soil temperature measurements, and it may be used
anywhere a reliable, low-cost temperature sensor is required. The sensor is epoxy-encapsulated in a vinyl cap. The
External Temperature Sensor uses a precision platinum wire thermistor as a sensor. The thermistor produces a
resistance change proportional to temperature.
To ensure accurate readings when measuring outdoor air temperature, the External Temperature Sensor should be
shielded from direct sunlight and other sources of reflected or radiated heat. We recommend the use of a Davis
Radiation Shield (# 7714) or its equivalent for this purpose.
General
Sensor Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Platinum wire thermistor
Time Constant
In Still Air. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 seconds
In Liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 seconds
Attached Cable Length . . . . . . . . . . . . . . . . . . . . . . . . . . 25' (7.6 m)
Note: There is no absolute maximum cable length. Increasing the cable length above 300' (90 m) causes an increased measurement error at
a rate of approximately +0.06°F (+0.03°C) per 100' (30 m) at 136°F (60°C) and +0.012°F (+0.006°C) per 100' (30 m) at 77°F (25°C).
Cable Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-conductor, 26 AWG
Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modular connector (RJ-11)
Recommended Maximum Cable Length (see Note 1 below)300' (90 m) from Sensor to SIM
Housing Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Black Vinyl
Housing Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25" diameter x 1.25" long (6.5 mm diameter x 32 mm long)
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 oz. (128 g)
Console Data
Note: (These specifications apply to sensor output as converted by Davis Instruments weather station consoles.)
Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -50° to 140°F (-45° to 60°C)
Accuracy (see Note 2). . . . . . . . . . . . . . . . . . . . . . . . . . . ±1°F (±0.5°C) (typical)
Resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0° or 0.1°F or 1.0° or 0.1°C Celsius is converted from Fahrenheit and
rounded to the nearest 0.1° or 1°C
Sample and Display Update Interval . . . . . . . . . . . . . . . . 16 seconds (max)
WeatherLink® Data
Note: (These specifications apply to sensor output as logged and displayed by the WeatherLink.)
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average over archive interval
High and Low Temperature . . . . . . . . . . . . . . . . . . . . . . . Maximum and minimum values during archive interval
Input/Output Connections
Black & Red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Common
Green & Yellow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature (variable resistance to common); 10KOhm, nominal