Data Sheet
7/10/2018 Precision Voltage Sensor - 1135_0B at Phidgets
https://www.phidgets.com/?tier=3&catid=16&pcid=14&prodid=1067 3/4
Version number: corresponds to the rmware version your Phidget is running. If your Phidget is listed in red, your rmware is out of date. Update the
rmware 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 Input
Double-click on a Voltage 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 1135 from the
Sensor Type
drop-down menu. The example will now convert the voltage into differential voltage (V) automatically. Converting the
voltage to differential voltage (V) is not specic to this example, it is handled by the Phidget libraries, with functions you have access to when you begin
developing!
Technical Details
General
The 1135 measures the differential voltage between the input terminals and outputs the difference proportionally. The maximum differential voltage that can be
measured accurately is ±30V. When the positive and negative inputs are equal, the voltage output value is 2.5V. When the positive input is 30V greater than the
negative input, the voltage output is 4.5V and when the positive input is 30V less than the negative input, the voltage output is 0.5V.
When measuring voltage levels below 5V, you'll have more accuracy if you connect the leads directly to the voltage input of the HUB0000 (or compatible product).
Since the 1135 can measure a differential voltage, the common mode rejection (CMR) is an important specication. CMR refers to the amount of voltage that both
input terminals of a differential amplier can be offset without affecting the output gain. For example, if the positive terminal sees a voltage of 7V and the negative
terminal sees a voltage of 5V, then the CMR would be 5V and would output a value of 2V at unity gain. For the 1135, it is able to measure the differential voltage of
±10V with a CMR of 40V while keeping the accuracy within 2%. Please note that the error specications do not include the error introduced by the Analog to Digital
Conversion on the Analog Input. (if you are using the 1135 with a PhidgetInterfaceKit) The majority of error introduced by the Analog to Digital conversion is from
the error in the voltage reference (0.5% max), and the limitation of resolution in the analog-to-digital converter. The best accuracy can be achieved by using a 2 or
more point calibration of your system - effectively calibrating the 1135 and the PhidgetInterfaceKit in a single step. If you are calibrating, be sure to use a good
quality multimeter to determine the voltage being applied.
Formulas
The Phidget libraries can automatically convert sensor voltage into differential voltage (V) by selecting the appropriate SensorType. See the Phidget22 API for
more details. The Formula to translate the analog voltage returned by the 1135 into differential voltage is:
where V is dened as V - V , and V is the voltage returned by the 1135. For maximum accuracy, measure the sensor voltage when measuring a 0V
source and replace the "2.5" in this equation with the zero value that you've measured.
V
diff
=
V
s
ens
− 2.5
0.0681
diff positive negative sens