Airflow Meter vs Differential Pressure Meter for Data Centre Cooling Malaysia
A server room may show a normal average temperature while some network racks receive insufficient cooling air.
To investigate the problem correctly, technicians must determine whether they need to measure air velocity or pressure difference.
An airflow meter and a differential pressure meter are both useful for data-centre cooling inspection, but they measure different conditions and should not be treated as interchangeable instruments.
What Is an Airflow Meter?
An airflow meter, also known as an anemometer, measures air velocity.
Depending on the instrument and application, it may be used at:
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Air-conditioning outlets
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Ventilation grilles
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Perforated raised-floor tiles
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Server-rack air intakes
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Server-rack exhaust areas
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Cooling-unit outlets
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Air ducts
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Hot and cold aisles
It helps answer:
“How fast is the air moving at this location?”
What Is a Differential Pressure Meter?
A differential pressure meter measures the pressure difference between two locations.
It may be used to compare:
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Raised floor and server room
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Cold aisle and surrounding area
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Server room and corridor
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Upstream and downstream of a filter
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Supply and return-air sections
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Contained aisle and adjacent space
It helps answer:
“What is the pressure difference between these two points?”
Airflow Meter Versus Differential Pressure Meter
| Inspection requirement | Airflow meter | Differential pressure meter |
|---|---|---|
| Measure air velocity | Yes | No |
| Check airflow from a grille | Yes | No |
| Compare pressure between two rooms | No | Yes |
| Measure pressure across a filter | No | Yes |
| Investigate weak airflow at a rack | Yes | Supporting measurement |
| Check raised-floor pressure | Limited | Yes |
| Compare cooling outlets | Yes | Limited |
| Assess room pressurisation | No | Yes |
For some cooling investigations, both instruments are required.
Why Is Airflow Important in a Data Centre?
Cooling equipment may operate normally while air fails to reach the intended racks.
Poor airflow may cause:
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High rack-inlet temperature
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Hotspots at the top of racks
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Hot-air recirculation
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Uneven cooling
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Repeated temperature alarms
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Server fans operating continuously
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Higher energy consumption
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Reduced equipment reliability
Airflow measurement provides evidence that cooling air reaches the required locations.
Why Is Differential Pressure Important?
Pressure differences influence how air moves between spaces.
Incorrect pressure may contribute to:
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Weak airflow through raised-floor tiles
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Air moving in the wrong direction
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Hot and cold air mixing
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Containment leakage
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Reduced cooling efficiency
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Dust entering the server room
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Unstable room conditions
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Poor filter performance
The required pressure relationship depends on the facility and cooling-system design.
Where Should Airflow Be Measured?
Cooling-Unit Outlet
Measure airflow at several points across the outlet rather than relying on one centre reading.
Cooling-Unit Intake
The intake measurement can support comparison with the outlet and help identify restrictions.
Perforated Raised-Floor Tiles
Compare tiles serving:
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High-load racks
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Low-load racks
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Problem areas
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Locations near and far from cooling units
Rack Front
Measure near the equipment air intake at:
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Bottom
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Middle
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Top
Rack Rear
Exhaust-air measurement can support investigation of heat removal and recirculation.
Hot and Cold Aisles
Measurements help determine whether air follows the intended path.
Where Should Differential Pressure Be Measured?
Raised Floor Versus Room
One pressure port is connected below the raised floor and the other measures the server-room side.
Record exactly which port is connected to each location.
Across a Filter
Measure upstream and downstream pressure to assess whether the filter may be restricting airflow.
Interpret the result according to the equipment manufacturer’s guidance.
Server Room Versus Corridor
This measurement helps determine the direction in which air is likely to move when openings or leakage paths are present.
Cold Aisle Versus Surrounding Space
For a contained aisle, pressure measurement may support assessment of containment performance.
How to Measure Airflow Correctly
Step 1: Define the Test Point
Record:
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Cooling unit
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Grille or tile
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Rack number
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Measurement height
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Distance from outlet
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Instrument orientation
Step 2: Confirm the Instrument Setting
Select the correct:
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Measurement unit
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Probe type
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Range
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Averaging mode
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Area setting where volume calculation is required
Step 3: Hold the Sensor Correctly
The sensor should face the airflow according to the instrument instructions.
Incorrect angle can affect the reading.
Step 4: Allow the Reading to Stabilise
Airflow often fluctuates. Avoid recording the first number displayed.
Step 5: Take Multiple Readings
Measure at several points across a large outlet or grille.
Calculate or record an average where appropriate.
Step 6: Compare With Previous Measurements
Use consistent locations and operating conditions.
A trend is often more useful than one isolated reading.
How to Measure Differential Pressure Correctly
Step 1: Identify Both Test Locations
Clearly define the high-pressure and low-pressure sides.
Step 2: Check the Tubing
Ensure the tubing is:
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Correctly connected
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Not bent
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Not blocked
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Not leaking
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Suitable for the measurement
Step 3: Zero the Instrument
Zero the meter according to the manufacturer’s procedure before connecting or measuring.
Step 4: Connect the Pressure Ports
Connect the positive and negative ports correctly.
A reversed connection may produce a negative result or opposite interpretation.
Step 5: Allow the Reading to Stabilise
Avoid recording while doors are opening, fans are changing speed or personnel are moving around the test point unless those events are part of the investigation.
Step 6: Record the Exact Conditions
Document:
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Both test locations
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Door position
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Cooling-unit status
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Fan status
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Filter condition
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Room operating condition
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Measurement unit
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Date and time
How to Investigate Weak Rack Cooling
Use this sequence:
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Measure room temperature and humidity.
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Check the rack inlet at different heights.
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Measure airflow at the rack front.
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Compare with nearby racks.
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Check the raised-floor tile or cooling outlet.
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Measure raised-floor pressure where applicable.
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Inspect for cable or equipment obstruction.
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Check blanking panels and containment.
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Scan the rack with a thermal camera.
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Correct the confirmed problem.
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Repeat all relevant measurements.
How to Check a Suspected Dirty Filter
Possible signs include:
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Reduced outlet airflow
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Increased fan noise
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Cooling unit operating for longer periods
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Repeated temperature alarms
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Higher pressure difference across the filter
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Visible dirt accumulation
Use:
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Differential pressure meter
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Airflow meter
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Temperature meter
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Visual inspection
Follow the cooling-unit manufacturer’s filter replacement limits.
Using a Thermal Camera With Airflow Measurements
The Noyafa NF-522 Thermal Camera can help locate:
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Warm areas at rack fronts
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Hot-air recirculation
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Uneven cooling patterns
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Hot equipment
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Cooling-motor hotspots
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Electrical problems
However, a thermal image does not directly measure air velocity.
Use an airflow meter to confirm whether insufficient air reaches the hotspot.
Using a Data Logger With Airflow Measurements
A data logger can reveal when rack temperature rises.
After identifying the time pattern:
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Measure airflow during the affected period
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Compare cooling-unit operation
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Check pressure conditions
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Inspect the rack thermally
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Review server load
The Elitech RC-5 can support temperature recording, while a suitable temperature-and-humidity logger such as the Elitech GSP-6 Pro may be used when both parameters are required.
Common Airflow Measurement Mistakes
Avoid:
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Measuring at only one point on a large grille
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Holding the sensor at the wrong angle
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Comparing readings taken at different distances
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Measuring under different fan conditions
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Blocking airflow with the technician’s body
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Recording an unstable reading
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Ignoring airflow direction
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Failing to document the exact position
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Comparing different units
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Assuming high air velocity always means good rack cooling
Common Differential Pressure Measurement Mistakes
Avoid:
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Reversing positive and negative ports
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Failing to zero the meter
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Using leaking or blocked tubing
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Recording no information about test locations
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Measuring while doors repeatedly open
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Ignoring fan operating condition
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Comparing readings in different units
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Assuming one pressure target applies to every data centre
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Failing to check manufacturer requirements
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Not repeating measurements after maintenance
Which Instrument Should You Buy?
Choose an airflow meter when the primary task is:
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Checking air velocity
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Comparing cooling outlets
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Testing rack airflow
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Measuring grille or tile output
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Investigating weak cooling
Choose a differential pressure meter when the primary task is:
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Comparing pressure between two spaces
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Checking raised-floor pressure
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Measuring pressure across filters
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Assessing room pressurisation
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Investigating containment pressure
Choose both when performing a complete cooling-system assessment.
Recommended Data Centre Cooling Tool Kit
A practical kit may include:
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Airflow meter
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Differential pressure meter
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Temperature and humidity meter
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Temperature data logger
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Temperature and humidity data logger
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Thermal imaging camera
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Sound level meter
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Vibration meter
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Clamp meter
Measure the Correct Cooling Parameter
An airflow meter and differential pressure meter provide different evidence.
The airflow meter shows how fast air moves at a particular location. The differential pressure meter shows the pressure relationship between two points.
Using the correct instrument—and documenting the exact test conditions—helps data-centre maintenance teams identify whether a cooling problem is caused by weak airflow, pressure imbalance, blocked filters or poor air distribution.
Contact MTM Precision
MTM Precision Sdn. Bhd.
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
🌐 Website: www.mtmpre.com.my
📧 Email: mtmpre@yahoo.com
📱 WhatsApp: +6016-660 7346
02 Sep 2026
