Wiring, Datalogger programming – Campbell Scientific CS505 Fuel Moisture Sensor User Manual

Page 8

CS505 Fuel Moisture Sensor

4. Wiring

Connections to Campbell Scientific dataloggers are given in Table 4-1. When
Short Cut for Windows software is used to create the datalogger program, the
sensor should be wired to the channels shown on the wiring diagram created
by Short Cut.

TABLE 4-1. Wiring for CS505

Color

Description

CR800/CR1000/
CR3000

CR10(X)/CR500/
CR510

CR23X

21X/CR7

red

power

12 V

black

ground

G G G

green

signal

Analog Channel

Pulse Channel

orange

enable

Control Port

clear ground

5. Datalogger Programming

This section is for users who write their own datalogger programs. A
datalogger program to measure this sensor can be created using Campbell
Scientific’s Short Cut Program Builder software. You do not need to read this
section to use Short Cut.

The CS505 has a built in enable circuit. When voltage on the enable lead is
less than 1.3 VDC, the sensor is off. When a voltage greater than 1.3 VDC,
commonly 5 VDC, is applied to the enable lead, the sensor is on. The output
signal is a

±2.5 volt square wave. Instruction P27 Period Average in the

CR500, CR510, CR10(X), and CR23X dataloggers measures the frequency of
the square wave with an analog channel.

Since fuel moisture doesn’t change very rapidly, the sensor is typically
measured only once an hour.

Instruction P27 measures the period of the output signal in microseconds. To
prepare for the polynomial, the output is scaled by 0.001. A second-order
polynomial is used to convert signal period to percent moisture content with
the following constants:

C0 = -220.14
C1 = 365.89
C2 = -114.96

or, expressed as a second order polynomial
y=-220.14+365.89x-114.96x