Mobile machinery relies on sensors to monitor pressure, temperature, position, fluid level, and other operating conditions.
However, many sensors do not send engineering values such as:
Pressure = 180 bar
Instead, they provide an electrical signal such as:
0–5 V
0–10 V
4–20 mA
Resistive signals
The mobile controller reads this electrical input and converts it into a meaningful engineering value that can be used by the control logic or displayed on an HMI.
This process is known as sensor signal scaling.
This article explains how signal scaling works and what engineers should consider when integrating analog sensors into mobile machinery.
Sensor signal scaling converts a raw electrical input into a physical value.
For example, consider a hydraulic pressure sensor with:
Output: 0–10 V
Measurement range: 0–250 bar
The controller needs to translate the voltage into pressure:
0 V → 0 bar
5 V → 125 bar
10 V → 250 bar
The resulting pressure value can then be used for:
Hydraulic control
Machine protection logic
HMI visualization
Alarms
Data logging
Diagnostics
A typical signal path is:
Pressure Sensor
↓
0–10 V
↓
Mobile Controller
↓
Signal Scaling
↓
0–250 bar
↓
Control Logic / HMI
Mobile machinery uses several types of analog sensor signals.
Common in position, pressure, and other electronic sensors.
The controller measures the input voltage and converts it according to the sensor's specified range.
Often used for pressure, position, level, and other analog measurements.
For example:
0 V → 0 bar
10 V → 400 bar
Current-loop sensors are widely used in industrial and mobile applications.
For example:
4 mA → 0 bar
12 mA → 150 bar
20 mA → 300 bar
One advantage of 4–20 mA is that the minimum measurement value is represented by 4 mA rather than 0 mA.
This makes it possible to distinguish certain wiring or sensor faults from a valid zero measurement.
Many analog sensors have a linear relationship between electrical output and physical measurement.
The basic scaling equation is:
Engineering Value = (Input − Input Min) × (Output Range / Input Range) + Output Min
Consider a 0–10 V pressure sensor measuring 0–250 bar.
If the controller reads 6 V:
Pressure = (6 − 0) × (250 / 10)
Pressure = 150 bar
The controller therefore converts the raw 6 V signal into a pressure value of 150 bar.
In practice, this calculation is usually implemented in the controller application rather than performed manually.
A 4–20 mA sensor requires the same basic principle, but its measurement does not begin at zero current.
Suppose a pressure sensor has:
4 mA = 0 bar
20 mA = 400 bar
The useful current range is:
20 − 4 = 16 mA
If the controller measures 12 mA:
4 mA 12 mA 20 mA
│ │ │
0 bar 200 bar 400 bar
The scaled pressure is approximately 200 bar.
This value can then be used throughout the machine control software.
The 4 mA offset provides an additional advantage.
Consider a pressure sensor whose valid operating signal begins at 4 mA.
If the controller measures:
4 mA → valid minimum pressure
but receives a value close to:
0 mA → possible wiring or sensor problem
the software can distinguish between a legitimate zero measurement and certain abnormal electrical conditions.
A simplified diagnostic strategy might be:
Normal Range
4–20 mA
↓
Use Scaled Value
Below Expected Range
↓
Possible Sensor / Wiring Fault
The exact thresholds should be based on the sensor specification and controller input characteristics.
Internally, a controller may first receive a raw input value rather than a directly usable physical measurement.
For example:
Analog Input
↓
Raw Value
↓
Scaling
↓
Pressure = 185 bar
Using engineering units makes the application easier to understand.
Instead of writing control logic based on an arbitrary raw number, engineers can work with values such as:
185 bar
72 °C
65%
2.4 m
850 rpm
This also makes troubleshooting and HMI configuration easier.
Scaling should not be the only function applied to an analog input.
The controller should also evaluate whether the signal is within an expected range.
For example, if a 0–10 V sensor unexpectedly reports a voltage outside its intended operating range, the application may treat the signal as invalid.
A simplified process is:
Analog Signal
↓
Range Check
↙ ↘
Valid Invalid
↓ ↓
Scaling Fault
↓ ↓
Control HMI Warning
Possible causes of an invalid signal include:
Broken wiring
Loose connectors
Sensor failure
Short circuit
Incorrect supply voltage
Incorrect sensor configuration
This prevents an obviously abnormal input from being treated as a normal machine measurement.
Real-world analog signals are not always perfectly stable.
Electrical noise, vibration, pressure pulsation, and sensor characteristics can cause small fluctuations.
For example:
182 bar
185 bar
183 bar
187 bar
184 bar
If the control logic reacts directly to every small variation, machine behavior or HMI values may become unstable.
Depending on the application, the controller can apply signal filtering to smooth the measurement.
However, excessive filtering can introduce delay.
Therefore, engineers need to balance:
Signal stability vs response speed
A slowly changing fluid-level signal may tolerate more filtering than a pressure signal used in fast hydraulic control.
Once a signal has been scaled and validated, it can be used by the controller.
For example:
Pressure Sensor
↓
0–10 V
↓
Controller
↓
Scaling
↓
Pressure = 210 bar
↓
Control Logic
The application may then use the pressure value to:
Adjust a proportional valve
Trigger an alarm
Limit a hydraulic function
Change machine operating mode
Send data over CAN
Display the value on the HMI
This is why correct signal scaling is important: an incorrect conversion can affect multiple parts of the machine control system.
Scaled engineering values can also be transmitted to an HMI.
Instead of displaying:
Analog Input = 6.8 V
the operator can see:
Hydraulic Pressure: 170 bar
The HMI may also use the same value for:
Gauges
Warning indicators
Trend displays
Diagnostic pages
Operating limits
This makes machine information easier for operators and service technicians to understand.
Consider a hydraulic system using a 4–20 mA pressure sensor.
The complete data path could be:
Hydraulic Pressure
↓
4–20 mA Sensor
↓
Analog Input
↓
Mobile Controller
↓
Range Check
↓
Signal Scaling
↓
Pressure in bar
↙ ↘
Control HMI
Logic Display
If the signal is valid, the controller converts it into pressure.
If the signal is outside the expected electrical range, the controller can generate a sensor fault instead of using an unreliable pressure value.
This combines measurement, control, and diagnostics within the same system.
When integrating a sensor with a mobile controller, several parameters should be confirmed:
Sensor output type
Sensor measurement range
Controller input type
Minimum and maximum electrical signal
Minimum and maximum engineering value
Sensor supply requirements
Scaling parameters
Valid signal range
Fault thresholds
Required filtering
The sensor datasheet and controller input specifications should always be checked before configuration.
For example, a 4–20 mA sensor must be connected to an input designed or configured to measure the appropriate current signal.
Sensor signal scaling is an important part of mobile machine control.
Sensors often provide electrical signals such as 0–5 V, 0–10 V, or 4–20 mA, while the control system needs meaningful engineering values such as pressure, temperature, position, or level.
The basic process is:
Sensor Signal → Analog Input → Validation → Scaling → Engineering Value → Control Logic / HMI
Correct scaling allows the mobile controller to use sensor information consistently throughout the machine.
Combined with range checking, filtering, diagnostics, and HMI visualization, analog input processing provides the foundation for reliable sensor-based control in modern mobile machinery.
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