FNIRSI SG-003A for Pressure Flow Level and Temperature Transmitter Testing Malaysia
FNIRSI SG-003A for Pressure Flow Level and Temperature Transmitter Testing Malaysia
Can one portable signal generator help when troubleshooting pressure, flow, level and temperature transmitters?
If these instruments provide compatible industrial analog signals such as 4-20 mA, a signal generator can be useful for checking the receiving side of the control system.
The FNIRSI SG-003A Signal Generator can be considered for suitable PLC troubleshooting, loop checking and commissioning applications.
However, there is an important distinction:
Generating a 4-20 mA signal is not the same as physically calibrating pressure, flow, level or temperature.
This guide explains where the SG-003A can help and where additional test equipment may be required.
Why So Many Industrial Transmitters Use 4-20 mA
Industrial plants need to send process measurements from field instruments to control systems.
A typical signal path may be:
Process > Sensor > Transmitter > 4-20 mA > PLC > HMI
For a standard linear 4-20 mA range:
4 mA = 0%
8 mA = 25%
12 mA = 50%
16 mA = 75%
20 mA = 100%
The actual engineering value depends on the transmitter range.
1. Pressure Transmitter Testing
Pressure transmitters are commonly used for:
Compressed air
Water systems
Pumps
Hydraulic systems
Boilers
Chillers
Process pipelines
Filtration systems
Suppose a pressure transmitter is configured as:
0-10 bar = 4-20 mA
Expected values are:
4 mA = 0 bar
8 mA = 2.5 bar
12 mA = 5 bar
16 mA = 7.5 bar
20 mA = 10 bar
A known electrical test signal can help determine whether the PLC and HMI interpret the signal correctly.
Example: Pressure Transmitter Shows 6 Bar but PLC Shows 0 Bar
The transmitter appears to be operating.
But the PLC shows:
0 bar
Possible causes include:
Field wiring
Loop power
Wrong PLC terminal
Incorrect PLC configuration
Scaling
PLC analog input
A suitable known signal can help check the receiving side.
If the PLC responds correctly to known signals, investigate the transmitter and field circuit more closely.
Can the SG-003A Calibrate Pressure?
Not by itself.
Generating 4-20 mA does not create physical pressure.
A full pressure transmitter calibration may require:
Pressure source
Reference pressure instrument
Suitable electrical measurement
Calibration procedure
Traceability, where required.
The SG-003A is more relevant to suitable electrical signal-side troubleshooting and functional testing.
2. Flow Transmitter Testing
Flow transmitters may be used for:
Process water
Cooling water
Wastewater
Chemical processes
Utility systems
Compressed air
Suppose the configured range is:
0-100 m3/h = 4-20 mA
For a linear relationship:
4 mA = 0 m3/h
8 mA = 25 m3/h
12 mA = 50 m3/h
16 mA = 75 m3/h
20 mA = 100 m3/h
A known input can help check whether the PLC and HMI respond according to the intended scaling.
Flow Systems May Use Additional Calculations
Be careful when troubleshooting flow.
Some applications may use:
Square-root calculations
Totalizers
Correction factors
Density compensation
Custom engineering calculations
Therefore, a 50% electrical signal does not always mean every final displayed process value should simply show 50%.
Understand the control logic before diagnosing a fault.
Can the SG-003A Calibrate Actual Flow?
No, not by generating an electrical signal alone.
Physical flow calibration may require suitable flow reference equipment and procedures.
Signal simulation mainly helps evaluate the electrical receiving system.
3. Level Transmitter Testing
Level transmitters are widely used in:
Water tanks
Chemical tanks
Storage vessels
Wastewater systems
Process tanks
Utility systems
Suppose:
0-5 m = 4-20 mA
Expected values are:
4 mA = 0 m
8 mA = 1.25 m
12 mA = 2.5 m
16 mA = 3.75 m
20 mA = 5 m
These known values can be useful when checking PLC scaling and HMI display.
Example: Tank Is Half Full but HMI Shows 20%
If the level transmitter is intended to provide:
4-20 mA = 0-100%
then approximately:
12 mA = 50%
If the PLC displays 50% when receiving a known 12 mA test signal, the receiving side is responding correctly under the test condition.
Investigation can then move towards:
Level transmitter
Sensor installation
Field wiring
Transmitter configuration
Actual tank conditions
Level Is Not Always the Same as Volume
This is important.
A transmitter may measure liquid height.
But the HMI may display calculated tank volume.
For irregular tank shapes:
50% level may not equal 50% volume
The PLC may use a lookup table or tank-strapping calculation.
Always identify what the final displayed value represents.
Can the SG-003A Calibrate Physical Level?
Electrical signal simulation does not verify whether a level sensor accurately measures the real liquid level.
Physical verification may require another method depending on the level measurement technology and installation.
4. Temperature Transmitter Testing
Temperature transmitters are commonly used in:
HVAC
Boilers
Chillers
Ovens
Production equipment
Food processing
Chemical processes
Building services
Suppose a temperature transmitter is configured:
0-100掳C = 4-20 mA
Expected values are:
4 mA = 0掳C
8 mA = 25掳C
12 mA = 50掳C
16 mA = 75掳C
20 mA = 100掳C
Known signal testing can help verify the PLC and HMI scaling.
Temperature Sensor vs Temperature Transmitter
These are not always the same type of input.
A PLC may receive a direct sensor input such as:
Pt100
RTD
Thermocouple
Or the sensor may connect to a transmitter that converts the measurement into:
4-20 mA
These require different test approaches.
Do not assume that a 4-20 mA signal generator directly simulates every RTD or thermocouple input.
Check the actual signal type.
Can the SG-003A Calibrate Temperature?
Generating a 4-20 mA electrical signal does not create a known physical temperature.
Full temperature calibration may require suitable temperature reference equipment and procedures.
Again, separate:
Electrical signal testing
from
Physical measurement calibration
One Instrument, Four Different Applications
For compatible 4-20 mA receiving systems, the same basic troubleshooting principle can apply to:
Pressure
Flow
Level
Temperature
The engineering units change.
The troubleshooting concept remains similar.
Provide a known input and observe how the receiving system responds.
Example Comparison
For a standard midpoint:
Pressure: 0-10 bar
12 mA = 5 bar
Flow: 0-100 m3/h
12 mA = 50 m3/h
Level: 0-5 m
12 mA = 2.5 m
Temperature: 0-100掳C
12 mA = 50掳C
This makes the midpoint particularly useful during basic troubleshooting.
Why Test More Than One Point?
A single test point does not show the complete behaviour of the system.
For a linear 4-20 mA application, a useful functional sequence can be:
4 mA = 0%
8 mA = 25%
12 mA = 50%
16 mA = 75%
20 mA = 100%
This helps identify:
Scaling errors
Incorrect ranges
HMI calculation problems
Wrong engineering units
Unexpected non-linear processing
FNIRSI SG-003A for PLC Testing
For suitable applications, the FNIRSI SG-003A can support troubleshooting of the receiving side involving:
PLC analog inputs
HMI displays
Control panels
4-20 mA loops
Alarm logic
Commissioning
Factory maintenance
The key question is:
Does the PLC respond correctly when the input signal is known?
Example: Three Transmitters All Show Wrong Readings
Suppose a machine has:
Pressure transmitter
Flow transmitter
Temperature transmitter
All three readings suddenly appear wrong.
Before replacing three transmitters, consider whether they share:
The same PLC analog module
The same power supply
The same control panel
The same configuration change
Known-signal testing of individual channels can provide useful diagnostic information.
Example: Only One Transmitter Is Wrong
If several analog channels work correctly but one channel does not, investigate:
That transmitter
Its wiring
Its PLC channel
Its scaling
Its configuration
Comparing a problematic channel with a known working channel can help narrow the search.
Useful for Factory Maintenance Teams
Factories may have dozens of analog transmitters.
A portable signal generator can therefore support troubleshooting across many systems, including:
Pumps
Compressors
Boilers
Chillers
Water treatment
HVAC
Process equipment
Production lines
Storage tanks
This is one reason a signal generator can be more useful than buying it for only one transmitter.
Useful for System Integrators
System integrators may work with different transmitters on every project.
One project may involve pressure.
Another may involve tank level.
Another may involve temperature and flow.
If the PLC receiving systems use compatible analog signals, the same portable signal tool may support multiple commissioning tasks.
Signal Testing vs Formal Calibration
This distinction should always be clear.
Using known electrical signals to check PLC response is useful for:
Troubleshooting
Functional checking
Commissioning
Loop checking
Formal calibration may additionally require:
Traceable reference equipment
Specified accuracy
Measurement uncertainty
Documented procedures
Calibration certificates
Choose the instrument and procedure according to the actual requirement.
What Should You Check Before Buying?
Before purchasing the FNIRSI SG-003A, identify:
Transmitter output type
PLC input type
Required signal range
Loop power arrangement
Required accuracy
Whether you need source, measurement or both
Whether the work is troubleshooting or formal calibration
Then confirm that the instrument's supported functions match the application.
Important Safety Reminder
Before applying a simulated signal:
Review the wiring diagram
Confirm the input type
Check the permitted signal range
Identify the correct terminals
Confirm polarity
Understand the loop power arrangement
Check the PLC program
Determine what equipment may respond
Follow site isolation and safety procedures
A simulated pressure, flow, level or temperature signal can potentially activate:
Pumps
Valves
Motors
Fans
Heaters
Alarms
Interlocks
Automatic sequences
Always understand the control response before changing the input signal.
Looking for FNIRSI SG-003A in Malaysia?
MTM Precision Sdn Bhd supplies the FNIRSI SG-003A Signal Generator in Malaysia for pressure, flow, level and temperature transmitter signal troubleshooting, PLC testing, control-panel commissioning and factory maintenance applications.
Not sure whether your transmitter can be tested using the SG-003A?
Send us a photo of the transmitter nameplate, PLC analog input module, wiring terminals or wiring diagram through WhatsApp.
Tell us whether the application is pressure, flow, level or temperature and what problem you are trying to troubleshoot.
We can help evaluate whether the FNIRSI SG-003A is suitable for your application.
MTM Precision Sdn Bhd
Showroom & Service Centre
No 29-1 & 2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my
Serving customers across Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.
04 Oct 2026
