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1072_0_Product_Manual - February 24, 2011 2:52 PM
Analog Inputs
Using the Analog Inputs with Sensors provided by Phidgets
Analogs Inputs are used to interface many different types of sensors. Each Analog Input provides power (Nominal
+5VDC), ground, and an analog voltage return wire driven by the sensor to some voltage. The PhidgetInterfaceKit
continuously measures this return voltage and reports it to the application.
Analog Inputs are used to measure continuous quantities, such as temperature, humidity, position, pressure, etc.
Phidgets offers a wide variety of sensors that can be plugged directly into the board using the cable included with
the sensor.
Using the Analog Inputs with your own sensors
For users who wish to interface their own sensors, we describe the Analog Inputs here.
Mechanical
Each Analog Input uses a 3-pin, 0.100 inch pitch locking connector. Pictured here is a
plug with the connections labeled. The connectors are commonly available - refer to
the Table below for manufacturer part numbers.
Cable Connectors
Manufacturer
Part Number
Description
Molex
50-57-9403
3 Position Cable Connector
Molex
16-02-0102
Wire Crimp Insert for Cable Connector
Molex
70543-0002
3 Position Vertical PCB Connector
Molex
70553-0002
3 Position Right-Angle PCB Connector (Gold)
Molex
70553-0037
3 Position Right-Angle PCB Connector (Tin)
Molex
15-91-2035
3 Position Right-Angle PCB Connector - Surface Mount
Note: Most of the above components can be bought at
www.digikey.com
Electrical
The maximum total current consumed by all Analog Inputs should be
limited to 400mA.
The analog measurement is represented in the software through the
SensorValue as a value between 0 and 1000. A sensor value of 1 unit
represents a voltage of approximately 5 millivolts. The RawSensorValue
property brings out a 12-bit value (0-4095) for users who require
maximum accuracy. Please note that the sampling is actually done with
an oversampled 10-bit ADC, but reported as a 12-bit value to allow
future expansion.
Ratiometric Configuration
The group of Analog Inputs can be collectively set to Ratiometric mode from software using the Ratiometric
property. If you are using a sensor whose output changes linearly with variations in the sensor’s supply voltage
level, it is said to be ratiometric. Most of the sensors sold by Phidgets are ratiometric (this is specified on the web
product page and in the sensor’s product manual).
1
1
2
2
3
3
4
4
D
D
C
C
B
B
A
A
20pF
1K
1M
+V
ANALOG
GROUND
Phidget
Analog
Input x1
Detail of Analog Input
INPUT
5V PW R
1K
SAMPL ING SWITCH
ANALOG
GROUND
INPUT
5V PW R
Phidget
Analog
Input
4K
Sensing the value of a variable resistance sensor
FSR
In this case, an FSR (force sensitive resistor) is shown.
1K
ANALOG
GROUND
INPUT
5V PW R
Phidget
Analog
Input
Sensing the position of a potentiometer
ANALOG
GROUND
INPUT
5V PW R
Phidget
Analog
Input
Interfacing to an arbitrary sensor
GND
3
VOUT
2
VCC
1
100nF
1K
100nF
Note the use of power supply decoupling and the RC Filter on the output.
The RC filter also prevents VOUT from oscillating on many sensors.
Technical
