A Ratiometric pressure sensor typically has a supply voltage of 3V to 5V .They will have a voltage output that is proportional to the supply voltage.
This makes Ratiometric an ideal output type for
- IoT
- Battery powered projects
- Embedded Systems
- Arduino
- Low power systems.
Key rules for Ratiometric pressure sensors to remember are
- Output is 10% to 90% of the supply.
- Low Power.
- If the supply Voltage changes the output value will change.
Ratiometric output is becoming increasingly popular and is a common choice to read pressure with embedded and electronics design engineers.
Ratiometric connections
Ratio metric is a voltage output which requires at least 3 connections or wires
What is Ratiometric output Voltage.
Keynote to remember the output Voltage is proportional to the Supply Voltage.
- Zero pressure – output Voltage 10% of the supply voltage
- Midpoint pressure – output Voltage is 50% of the supply voltage
- Full scale pressure – output Voltage 90% of the supply voltage
Ratiometric Span
The voltage span also depends on the supply voltage, for a typical 5V system the span is 4V. The below diagram illustrate the span relationship to the supply voltage.
The span is calculated by the formula SpanVoltage =ZeroVoltage – FullScaleVoltage
Formula for Voltage output
| Applied Pressure | Voltage Output |
| 0% of Range | Supply Voltage X 0.1 |
| 50% of Range | Supply Voltage X 0.5 |
| 100% of Range | Supply Voltage X 0.9 |
Ratiometric Output to Pressure Equation
Example 1 5V 0-10 bar Ratiometric pressure sensor
Supply = 5V
Pressure Range = 0-10 Bar
Pressure Span = 10 Bar
Voltage Output = 10% of Supply to 90% of Supply
Voltage Output = 0.5V to 4.5V
Voltage Span = ZeroVoltage-FullScaleVoltage
Voltage Span = 4.5V – 0.5V = 4V
How to calculate pressure from Ratiometric voltage
If the output voltage is 2.5V using the formula above we have.
These equations are simple enough for most Microcontrollers making them a wise chose for embedded systems.
Example 2 3V 1-5 bar Ratiometric pressure sensor
Supply = 3V
Pressure Range = 1-5 Bar
Pressure Span = 4 Bar
Voltage Output = 10% of Supply to 90% of Supply
Voltage Output = 0.3V to 2.7V
Voltage Span = ZeroVoltage-FullScaleVoltage
Voltage Span = 2.7V – 0.3V = 2.4V
How to calculate pressure from Ratiometric voltage
If the output voltage is 1.24V using the Ratiometric output to Pressure equation we have
Mechanics
The Ratiometric pressure sensors are supplied as standard below but can be customised upon request
IP65 Cable outlet dimensions
Dimensional drawing of an IP65 Ratiometric pressure sensor. The cable length can varary from 1-5m
M12 Ratiometric Dimensions
Dimensional drawing of a Ratiometric pressure sensor with an M12 connector