Analog Input Guide: Difference between revisions

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[[Category:Primer]]


Voltage Inputs are used to interface many different types of sensors, such as temperature, humidity, position, or pressure sensors.  
Analog Inputs are used to interface many different types of sensors, such as temperature, humidity, position, or pressure sensors. There are three classes of Phidget products that can be used with these sensors:
Phidget InterfaceKits such as the [{{SERVER}}/products.php?product_id=1018 1018 - PhidgetInterfaceKit 8/8/8] have multiple voltage inputs.
 
Each voltage input provides power (Nominal +5VDC), ground, and an analog voltage return wire driven by the sensor to some voltage.   
* Phidget InterfaceKits such as the [{{SERVER}}/products.php?product_id=1018 1018 - PhidgetInterfaceKit 8/8/8] have multiple voltage inputs.  
 
* The ports on a Phidget {{VINTHub}} can be used to read sensors like an analog input. See the page on [[Phidget Connectors]] for more information
 
* Some VINT devices like the [{{SERVER}}/products.php?product_id=DAQ1000 DAQ1000] add analog inputs to your VINT Hub.
 
Each analog input provides power (Nominal +5VDC), ground, and an analog voltage return wire driven by the sensor to some voltage.   
The Interface Kit continuously measures this return voltage and reports it to the application.
The Interface Kit continuously measures this return voltage and reports it to the application.


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==Electrical Specifications==
==Electrical Specifications==


[[Image:analoginputcircuit.jpg|right|thumb|300px|link=|Schematic for a Phidgets voltage input.]]
[[Image:analoginputcircuit.jpg|right|thumb|300px|link=|Schematic for a Phidgets analog input.]]


The maximum total current consumed by all voltage inputs should be limited to 400mA.
The maximum total current consumed by all analog inputs should be limited to 400mA.
The voltage measurement is represented in the software through the SensorValue as a value between 0 and 1000.   
The voltage measurement is represented in the software through the Voltage property as a value between 0 and 5 volts.   
5V corresponds to a high sensor value, and 0V corresponds to zero sensor activity.
5V corresponds to a high sensor value, and 0V corresponds to zero sensor activity.
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.


One side effect of this oversampling is that very low noise signals will not get full resolution from the ADC without dithering noise injected into the signal. 
The analog inputs on Phidgets InterfaceKits are designed for a maximum of 5V.  More than this will cause unpredictable behaviour and could damage the board.  
 
The voltage inputs on Phidgets interface kits are designed for a maximum of 5V.  More than this will cause unpredictable behaviour and could damage the board.  
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==Ratiometric Configuration==
==VoltageInput and VoltageRatioInput==
The group of voltage inputs can be collectively set to Ratiometric mode from software using the Ratiometric property. 
Each analog input can be opened as either a VoltageInput object or a VoltageRatioInput in software.   
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).   


Setting Ratiometric causes the reference to the internal Analog to Digital Converter to be set to the power supply voltage level.
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, and you should use the VoltageRatioInput object. Most of the sensors sold by Phidgets are ratiometric (you can find this in the specification table on the product page for your sensor). Opening the input as a VoltageRatioInput causes the reference to the internal Analog to Digital Converter to be set to the power supply voltage level. The VoltageRatio property ranges from 0.0 to 1.0, which denotes the ratio of the sensor voltage to the supply voltage. For example, if the supply is 5V and the sensor is outputting 2.5V, the VoltageRatio will be 0.5.  
When Ratiometric is enabled, the maximum voltage returned on the voltage input should be the +5V nominal power provided by the PhidgetInterfaceKit.


If Ratiometric is false, the ADC reference is set to a 5.0V 0.5% stable voltage reference.
If you open the input using the VoltageInput object, the ADC reference is set to a 5.0V 0.5% stable voltage reference. This will allow you to correctly interface with sensors that output a set voltage range regardless of variations in the power you supply to it.  
The maximum voltage returned on the voltage input should be maximum 5.0V. 
Note that the voltage input power supply voltage is not
affected by the setting of the Ratiometric property.


The ratiometric setting of the interface kit applies to all inputs. Trying to read a sensor with the wrong ratiometric setting will result in incorrect readings. However, it is technically possible to use both ratiometric and non-ratiometric sensors at the same time if you poll for one sensor and then switch the kit's ratiometric setting before polling the other sensor.
Trying to read a sensor using the wrong software object will result in incorrect readings.  
When switching ratiometric mode on and off, you need to include a short delay (50ms should be more than enough) before you begin reading values in.  This gives the device time to react.


==Factors that can affect Accuracy==
==Factors that can affect Accuracy==


*'''High Output Impedance''' - Sensors that have a high output impedance will be distorted by the 900K input impedance of the voltage input.   
*'''High Output Impedance''' - Sensors that have a high output impedance will be distorted by the input impedance of the analog input.   
If your output impedance is high, it is possible to correct for this distortion to some extent in your software application.
If your output impedance is high, it is possible to correct for this distortion to some extent in your software application.


*'''Power Consumption''' - Phidget cables have some resistance, and the power consumption of the sensor will cause the sensor to have a slightly different ground from the voltage input on the PhidgetInterfaceKit.  The more power consumed by the sensor, and the longer the Phidget cable, the more pronounced this effect will be.
*'''Voltage Drop''' - Phidget cables have some resistance, which can cause voltage to drop across particularly long lengths of cable. For ratiometric sensors in particular, this can affect accuracy. Long cables also potentially expose the line to a greater amount of interference from surrounding electronics.  


*'''Intrinsic Error In Sensors''' - For many sensors, the error is quite predictable over the life of the sensor, and it can be measured and calibrated out in software.
*'''Intrinsic Error In Sensors''' - For many sensors, the error is quite predictable by testing it alongside a more accurate sensor, and can be calibrated out in software.


*'''Non-Ratiometric Configuration''' - Voltage Reference error.  The 5.0VDC voltage reference is accurate to 0.5%.   
*'''Voltage Reference''' - Voltage Reference error.  The 5.0VDC voltage reference is accurate to 0.5%.   
This can be a significant source of error in some applications, but can be easily measured and compensated for.
This can be a significant source of error in some applications, but can be easily measured and compensated for.


Some sensors are accurate enough to take advantage of using the raw sensor value.
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If you want maximum accuracy, you can use the RawSensorValue property. 
To modify the formula, substitute (SensorValue) with (RawSensorValue / 4.095)


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==Changing the Data Interval==
You can change the data interval for each VoltageInput or VoltageRatioInput object in software.


==Changing the Data Rate==
For analog inputs, 8 ms is the maximum transmission rate. This limit is set by the USB processor we use, so there isn't much you can do to get around it.  
You can change the data rate for each voltage input from 1 millisecond to 1 second.
By default, the voltage input data set is sent to the PC every 8ms.
For voltage inputs, 8 ms is the maximum transmission rate. This limit is set by the USB processor we use, so there isn't much you can do to get around it.  


For values less than 8 ms, the data rate sets the sampling rate, not the transmission rate.  
For values less than 8 ms, the data interval sets the sampling rate, not the transmission rate.  
If, for example, you set the data rate to 1ms, you will receive a packet containing 8 miliseconds worth of 1 ms samples every 8ms.  
If, for example, you set the data interval to 1ms, you will receive a packet containing 8 miliseconds worth of 1 ms samples every 8ms.  
Setting the data rate at 1, 2, or 4ms will not allow you to react to received sensor data any faster than every 8ms;  
Setting the data interval to 1, 2, or 4ms will not allow you to react to received sensor data any faster than every 8ms;  
You will simply get more data samples within the 8ms. This feature is useful if you need to log sensor data at less than 8 ms resolution but don't need to react to it in real-time.
You will simply get more data samples within the 8ms. This feature is useful if you need to log sensor data at less than 8 ms resolution but don't need to react to it in real-time.


Setting the data rate of the voltage inputs is an alternative to setting the [[#Changing the Sensitivity/Change Trigger|sensitivity]]. Setting one of these values will disable the other, since you can either have events trigger on a regular interval, or on a minimum change.
Setting the data interval of the analog inputs is (in some ways) an alternative to setting the [[#Changing the Change Trigger|change trigger]]. For details on how these two properties interact with one another, have a look at the [[Data Interval/Change Trigger]] page.  


When the Data rate is set at a multiple of 8 ms, the data rate sets both the sampling rate and the transmission rate.
There is also a limit as to how many channels can be set at a high sampling rate, since you will, at one point run out of bandwidth.   
There is also a limit as to how many channels can be set at a high sampling rate, since you will, at one point run out of bandwidth.   
We estimate that you can set up to 4 channels to 1ms or you could set all channels to 2ms.   
We estimate that you can set up to 4 channels to 1ms or you could set all channels to 2ms.   
You can't turn channels off entirely to save bandwidth, you can only set them to a slower data rate.
You can't turn channels off entirely to save bandwidth, you can only set them to a longer data interval.
You will get an error when you exceed the available bandwidth, warning you of lost data samples.  
You will get an error when you exceed the available bandwidth, warning you of lost data samples.  


Note that data rate is limited to at most 16ms when opening over the Phidget Webservice.  
Note that data interval is limited to at most 16ms when opening over the Phidget Webservice.  
Actual data rate will depend on network latency.
Actual data interval will depend on network latency.
 
The method to change data rate is different in each API [[Software_Overview#Language_Support|(See your API for more information)]]. For example, here's how you would change data rate in C#:


<div class="source">
The method to change data interval is slightly different in each programming language; see the {{Phidget22API}} for more information.
<syntaxhighlight lang=csharp>


// Create a new InterfaceKit object
==Changing the Change Trigger==
InterfaceKit IFK = new InterfaceKit();


// Open a local InterfaceKit over the webservice
You can change the change trigger of a sensor using the VoltageChangeTrigger or VoltageRatioChangeTrigger properties in software. You can think of change trigger as a minimum amount of change in voltage needed to register a change event in software. Whenever your sensor generates a new value, it will be compared to the change trigger. If the difference between the last triggered data point and the new data point is less than the change trigger value, no event will be generated.
IFK.open("localhost",5001);


// Change the data rate of voltage input zero to 8ms (125 samples/sec)
Setting the change trigger of an analog input is an (in some ways) an alternative to setting the [[#Changing the Data Interval|data interval]]. For details on how these two properties interact with one another, have a look at the [[Data Interval/Change Trigger]] page.  
IFK.sensors[0].DataRate = 8;


</syntaxhighlight>
The method to change the change trigger is slightly different in each programming language; see the {{Phidget22API}} for more information.
</div>
<br>


==Changing the Sensitivity/Change Trigger==
==Connecting non-Phidget devices to the Analog Inputs==
 
Here are some circuit diagrams that illustrate how to connect various non Phidgets devices to the analog inputs on your Phidget.
You can change the sensitivity of a sensor using our API. You can think of sensitivity as a minimum amount needed to register a change (thus triggering a SensorChangeEvent). Whenever your sensor generates a new value, it will be compared to the sensitivity. If the difference between the previous data point and the new data point is less than the sensitivity value, no event will be generated. Sensitivity is measured in sensorvalue, which is a value between 1-1000 that represents the full range of a sensor. Setting the sensitivity of an voltage input is an alternative to setting the [[#Changing the Data Rate|data rate]]. Setting one of these values will disable the other, since you can either have events trigger on a regular interval, or on a minimum change.
 
The method to change sensitivity/change trigger is different in each API [[Software_Overview#Language_Support|(See your API for more information)]]. For example, here's how you would change sensitivity in C#:
 
<div class="source">
<syntaxhighlight lang=csharp>
 
// Create a new InterfaceKit object
InterfaceKit IFK = new InterfaceKit();
 
// Open a local InterfaceKit over the webservice
IFK.open("localhost",5001);
 
// Change the sensitivity of voltage input zero to "10".
IFK.sensors[0].Sensitivity = 10;
 
</syntaxhighlight>
</div>
<br>
 
==Connecting non-Phidget devices to the Voltage Inputs==
Here are some circuit diagrams that illustrate how to connect various non Phidgets devices to the voltage inputs on your Phidget.


===Sensing the Value of a Variable Resistance Sensor===
===Sensing the Value of a Variable Resistance Sensor===
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[[Image:arbitrary_sensor.jpg|right|link=|thumb|250px|Schematic for connecting to a sensor.]]
[[Image:arbitrary_sensor.jpg|right|link=|thumb|250px|Schematic for connecting to a sensor.]]


Normally, you can connect a sensor directly to the voltage input as long as it has a 0-5V range (or smaller). However, if the sensor is not designed to send its signal across a long cable, you may need to add components as shown in the image.
Normally, you can connect a sensor directly to the analog input as long as it has a 0-5V range (or smaller). However, if the sensor is not designed to send its signal across a long cable, you may need to add components as shown in the image.


Note the use of power supply decoupling and the RC Filter on the output.  
Note the use of power supply decoupling and the RC Filter on the output.  
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[[File:33vsensor.jpg|thumb|200px|link=|Interfacing a 3.3V Sensor using a 3.3V power supply.<br/>[[Media:33vsensor.jpg|Full-sized Image]]]]
[[File:33vsensor.jpg|thumb|200px|link=|Interfacing a 3.3V Sensor using a 3.3V power supply.<br/>[[Media:33vsensor.jpg|Full-sized Image]]]]


When using a 3.3V sensor with the voltage input of a Phidget InterfaceKit, the main challenge is generating the 3.3V supply. You can either buy a 3.3V power supply, or you can buy a voltage regulator to convert the 5V line on the voltage input to a 3.3V line, as illustrated in the diagrams. You can also use a second voltage input to monitor the output of the 3.3V supply on the regulator. Note that SensorValue will still be equal to the input voltage multiplied by 200, so a 3.3V sensor will saturate at a SensorValue of 667 instead of the usual 1000.
When using a 3.3V sensor with the analog input of a Phidget InterfaceKit, the main challenge is generating the 3.3V supply. You can either buy a 3.3V power supply, or you can buy a voltage regulator to convert the 5V line on the analog input to a 3.3V line, as illustrated in the diagrams. You can also use a second analog input to monitor the output of the 3.3V supply on the regulator.  
 
If the sensor is ratiometric, you can determine the measured value of the sensor expressed as a percentage of the maximum value by dividing the sensor value of voltage input 0 by voltage input 1. For example, if voltage input 1 measures a SensorValue of 667, and voltage input 0 measures a SensorValue of 133, then you know that the sensor's measured value is twenty percent of the sensor's maximum value.


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===Interfacing 4-20mA Sensors===
===Interfacing 4-20mA Sensors===


You can use the [{{SERVER}}/products.php?product_id=1132 1132 - 4-20mA Sensor Interface] to read a 4-20mA sensor with an voltage input. For more information on 4-20mA sensors, see the [[4-20mA Sensor Interface Primer]].
You can use the [{{SERVER}}/products.php?product_id=1132 1132 - 4-20mA Sensor Interface] to read a 4-20mA sensor with an analog input. For more information on 4-20mA sensors, see the [[4-20mA Sensor Interface Primer]].


==List of Devices with Voltage Input==
==List of Devices with an Analog Input==


{{:Devices with Analog Inputs}}
{{:Devices with Analog Inputs}}

Revision as of 19:58, 10 April 2017


Analog Inputs are used to interface many different types of sensors, such as temperature, humidity, position, or pressure sensors. There are three classes of Phidget products that can be used with these sensors:

  • The ports on a Phidget VINT Hub can be used to read sensors like an analog input. See the page on Phidget Connectors for more information
  • Some VINT devices like the DAQ1000 add analog inputs to your VINT Hub.

Each analog input provides power (Nominal +5VDC), ground, and an analog voltage return wire driven by the sensor to some voltage. The Interface Kit continuously measures this return voltage and reports it to the application.

Phidgets offers a wide variety of sensors that can be plugged directly into the board using the cable included with the sensor.

Mechanical Specifications

Analoginput.jpg

Each analog input uses a 3-pin, 0.100 inch pitch locking connector. Pictured here is a plug with the connections labeled.


The Phidget cables that are designed to plug into these inputs can be found here.


The connectors and pins they use are also commonly available (usually through digikey) - refer to the table below for manufacturer part numbers.

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


Electrical Specifications

Schematic for a Phidgets analog input.

The maximum total current consumed by all analog inputs should be limited to 400mA. The voltage measurement is represented in the software through the Voltage property as a value between 0 and 5 volts. 5V corresponds to a high sensor value, and 0V corresponds to zero sensor activity.

The analog inputs on Phidgets InterfaceKits are designed for a maximum of 5V. More than this will cause unpredictable behaviour and could damage the board.

VoltageInput and VoltageRatioInput

Each analog input can be opened as either a VoltageInput object or a VoltageRatioInput in software.

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, and you should use the VoltageRatioInput object. Most of the sensors sold by Phidgets are ratiometric (you can find this in the specification table on the product page for your sensor). Opening the input as a VoltageRatioInput causes the reference to the internal Analog to Digital Converter to be set to the power supply voltage level. The VoltageRatio property ranges from 0.0 to 1.0, which denotes the ratio of the sensor voltage to the supply voltage. For example, if the supply is 5V and the sensor is outputting 2.5V, the VoltageRatio will be 0.5.

If you open the input using the VoltageInput object, the ADC reference is set to a 5.0V 0.5% stable voltage reference. This will allow you to correctly interface with sensors that output a set voltage range regardless of variations in the power you supply to it.

Trying to read a sensor using the wrong software object will result in incorrect readings.

Factors that can affect Accuracy

  • High Output Impedance - Sensors that have a high output impedance will be distorted by the input impedance of the analog input.

If your output impedance is high, it is possible to correct for this distortion to some extent in your software application.

  • Voltage Drop - Phidget cables have some resistance, which can cause voltage to drop across particularly long lengths of cable. For ratiometric sensors in particular, this can affect accuracy. Long cables also potentially expose the line to a greater amount of interference from surrounding electronics.
  • Intrinsic Error In Sensors - For many sensors, the error is quite predictable by testing it alongside a more accurate sensor, and can be calibrated out in software.
  • Voltage Reference - Voltage Reference error. The 5.0VDC voltage reference is accurate to 0.5%.

This can be a significant source of error in some applications, but can be easily measured and compensated for.


Changing the Data Interval

You can change the data interval for each VoltageInput or VoltageRatioInput object in software.

For analog inputs, 8 ms is the maximum transmission rate. This limit is set by the USB processor we use, so there isn't much you can do to get around it.

For values less than 8 ms, the data interval sets the sampling rate, not the transmission rate. If, for example, you set the data interval to 1ms, you will receive a packet containing 8 miliseconds worth of 1 ms samples every 8ms. Setting the data interval to 1, 2, or 4ms will not allow you to react to received sensor data any faster than every 8ms; You will simply get more data samples within the 8ms. This feature is useful if you need to log sensor data at less than 8 ms resolution but don't need to react to it in real-time.

Setting the data interval of the analog inputs is (in some ways) an alternative to setting the change trigger. For details on how these two properties interact with one another, have a look at the Data Interval/Change Trigger page.

There is also a limit as to how many channels can be set at a high sampling rate, since you will, at one point run out of bandwidth. We estimate that you can set up to 4 channels to 1ms or you could set all channels to 2ms. You can't turn channels off entirely to save bandwidth, you can only set them to a longer data interval. You will get an error when you exceed the available bandwidth, warning you of lost data samples.

Note that data interval is limited to at most 16ms when opening over the Phidget Webservice. Actual data interval will depend on network latency.

The method to change data interval is slightly different in each programming language; see the Phidget22 API for more information.

Changing the Change Trigger

You can change the change trigger of a sensor using the VoltageChangeTrigger or VoltageRatioChangeTrigger properties in software. You can think of change trigger as a minimum amount of change in voltage needed to register a change event in software. Whenever your sensor generates a new value, it will be compared to the change trigger. If the difference between the last triggered data point and the new data point is less than the change trigger value, no event will be generated.

Setting the change trigger of an analog input is an (in some ways) an alternative to setting the data interval. For details on how these two properties interact with one another, have a look at the Data Interval/Change Trigger page.

The method to change the change trigger is slightly different in each programming language; see the Phidget22 API for more information.

Connecting non-Phidget devices to the Analog Inputs

Here are some circuit diagrams that illustrate how to connect various non Phidgets devices to the analog inputs on your Phidget.

Sensing the Value of a Variable Resistance Sensor

Schematic for connecting to an FSR.

In this diagram, an FSR (Force Sensitive Resistor) is shown.


Sensing the Position of a Potentiometer

Schematic for connecting to a potentiometer

This diagram shows how to monitor the position of a potentiometer.


Interfacing to an Arbitrary Sensor

Schematic for connecting to a sensor.

Normally, you can connect a sensor directly to the analog input as long as it has a 0-5V range (or smaller). However, if the sensor is not designed to send its signal across a long cable, you may need to add components as shown in the image.

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.


Interfacing 3.3V Sensors

Interfacing a 3.3V Sensor using a voltage regulator.
Full-sized Image
Interfacing a 3.3V Sensor using a 3.3V power supply.
Full-sized Image

When using a 3.3V sensor with the analog input of a Phidget InterfaceKit, the main challenge is generating the 3.3V supply. You can either buy a 3.3V power supply, or you can buy a voltage regulator to convert the 5V line on the analog input to a 3.3V line, as illustrated in the diagrams. You can also use a second analog input to monitor the output of the 3.3V supply on the regulator.


Interfacing 4-20mA Sensors

You can use the 1132 - 4-20mA Sensor Interface to read a 4-20mA sensor with an analog input. For more information on 4-20mA sensors, see the 4-20mA Sensor Interface Primer.

List of Devices with an Analog Input

Product # Name # of Analog Inputs Additional Features
1010 PhidgetInterfaceKit 8/8/8 Mini-Format 8 DIP-36 Package for compact and OEM applications, 8 Digital Inputs, 8 Digital Outputs
1011 PhidgetInterfaceKit 2/2/2 2 Compact USB Dongle Size, 2 Digital Inputs, 2 Digital Outputs
1018 PhidgetInterfaceKit 8/8/8 8 8 Digital Inputs, 8 Digital Outputs
1019 PhidgetInterfaceKit 8/8/8 w/6 Port Hub 8 8 Digital Inputs, 8 Digital Outputs, 6-port USB Hub
1065 PhidgetMotorControl 1-Motor 2 1 DC Motor control, 2 Digital Inputs, 1 Encoder Input
1073 PhidgetSBC3 8 Single Board Computer, 8 Digital Inputs, 8 Digital Output, 6-port USB Hub
1203 PhidgetTextLCD 8 LCD Character Screen, 8 Digital Inputs, 8 Digital Outputs
DAQ1000 8x Voltage Input Phidget 8 Connects to a VINT Hub

Phidget Cables

Product # Name
3002 Phidget Cable 60cm
3003 Phidget Cable 10cm
3004 Phidget Cable 350cm
3034 Phidget Cable 15cm
3038 Phidget Cable 120cm
3039 Phidget Cable 180cm

Connector Details

Analoginput.jpg

Each analog input uses a 3-pin, 0.100 inch pitch locking connector. Pictured here is a plug with the connections labeled.


The Phidget cables that are designed to plug into these inputs can be found here.


The connectors and pins they use are also commonly available (usually through digikey) - refer to the table below for manufacturer part numbers.

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


Non Phidgets 0-5V Sensors

In addition to Phidgets sensors, any sensor that returns a signal between 0 and 5 volts can be easily interfaced. Here is a list of interesting sensors that can be used with the PhidgetInterfaceKit 8/8/8. Note: these sensors are not “plug & play” like the sensors manufactured by Phidgets.


Sensors
Manufacturer Part Number Description
MSI Sensors FC21/FC22 Load cells - measure up to 100lbs of force
Humirel HTM2500VB Humidity sensors
Measurement Specialties MSP-300 Pressure sensors - ranges up to 10,000 PSI
Freescale Semiconductor MPXA/MPXH Gas Pressure Sensors
Allegro ACS7 series Current Sensors - ranges up to 200 Amps
Allegro A1300 series Linear Hall Effect Sensors - to detect magnetic fields
Analog TMP35 TMP36 TMP37 Temperature Sensor
Panasonic AMN series Motion Sensors
Honeywell FS01, FS03 Small, accurate Piezo-resistive load cells
AllSensors-Europe BARO-A-4V Barometric Pressure Sensor - 600 to 1,100 mbar

Note: Most of the above components can be bought at www.digikey.com

0-5V sensors often have their precision measured in mV/Unit. This value represents how many millivolts the sensor will output given a certain measured value. For example, a temperature sensor might output 1 mV per degree Celsius. You can use this value to build a formula so your program can convert it to the measured quantity. Some sensors can have their mV/Unit output changed, which allows you to tweak the sensor's full scale of measurement. Read your sensor's data sheet for conversion formulae and calibration information.

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