Getting Started

Welcome to the 1138 user guide! In order to get started, make sure you have the following hardware on hand:

• 1138 - Differential Air Pressure Sensor 50 kPa
• Any Phidget with a Voltage Ratio Input port, here are some compatible products. We will be using the VINT Hub for this guide.
• USB cable and computer
• Phidget cable

Next, you will need to connect the pieces:

1. Connect the 1138 to the HUB0000 with the Phidget cable.
2. Connect the HUB0000 to your computer with the USB cable.

Now that you have everything together, let's start using the 1138!

Using the 1138

Phidget Control Panel

In order to demonstrate the functionality of the 1138, we will connect it to the HUB0000, and then run an example using the Phidget Control Panel on a Windows machine.

The Phidget Control Panel is available for use on both macOS and Windows machines. If you would like to follow along, first take a look at the getting started guide for your operating system:

• Getting started with Windows
• Getting started with macOS

Linux users can follow the getting started with Linux guide and continue reading here for more information about the 1138.

First Look

After plugging in the 1138 into the HUB0000, and the HUB0000 into your computer, open the Phidget Control Panel. You will see something like this:

The Phidget Control Panel will list all connected Phidgets and associated objects, as well as the following information:

• Serial number: allows you to differentiate between similar Phidgets.
• Channel: allows you to differentiate between similar objects on a Phidget.
• Version number: corresponds to the firmware version your Phidget is running. If your Phidget is listed in red, your firmware is out of date. Update the firmware by double-clicking the entry.

The Phidget Control Panel can also be used to test your device. Double-clicking on an object will open an example.

Voltage Ratio Input

Double-click on a Voltage Ratio Input object in order to run the example:

General information about the selected object will be displayed at the top of the window. You can also experiment with the following functionality:

• Modify the change trigger and/or data interval value by dragging the sliders. For more information on these settings, see the data interval/change trigger page.
• Select the 1138 from the Sensor Type drop-down menu. The example will now convert the voltage into pressure (kPa) automatically. Converting the voltage to pressure (kPa) is not specific to this example, it is handled by the Phidget libraries, with functions you have access to when you begin developing!

Technical Details

General

The 1138 uses bipolar processing to provide an accurate, high level analog input signal that is proportional to the applied pressure. When the sensor is plugged in, the sensor voltage should default to about 0.2V, which corresponds to 0 kPa between the two ports.

Ports

The sensor comes with a positive top port and a negative bottom port. These ports have a diameter of 2.79mm to 3.30 mm (nominal 3mm). Take caution when connecting the pressure ports, this sensor only measures a positive pressure differential, and you could damage the sensor if you connect it in reverse. Ensure that the upper port is always at an equal or higher pressure than the lower port.

For hosing, we recommend using polyurethane tubing. We have had good results with 2.4mm ID tubing from EMI. In imperial measurement, 3/32” ID tubing is equivalent. This is available through laboratory supply stores such as Cole Parmer.

Formulas

The Phidget libraries can automatically convert sensor voltage into pressure (kPa) by selecting the appropriate SensorType. See the Phidget22 API for more details. The Formula to translate voltage ratio into Pressure is:

${\displaystyle {\text{Pressure (kPa)}}=({\text{VoltageRatio}}\times 55.56)-2.222}$

${\displaystyle {\text{Pressure (psi)}}=({\text{VoltageRatio}}\times 8.055)-0.322}$

Phidget Cable

The Phidget Cable is a 3-pin, 0.100 inch pitch locking connector. Pictured here is a plug with the connections labelled. The connectors are commonly available - refer to the Analog Input Primer for manufacturer part numbers.

What to do Next

• Programming Languages - Find your preferred programming language here and learn how to write your own code with Phidgets!
• Phidget Programming Basics - Once you have set up Phidgets to work with your programming environment, we recommend you read our page on to learn the fundamentals of programming with Phidgets.