How to Use a Differential Pressure Meter for Data Centre Cooling Inspection Malaysia

A differential pressure meter helps data-centre technicians compare air pressure between two locations.

It can support investigations involving raised-floor cooling, server-room pressure, aisle containment, dirty filters and uneven airflow.

A normal room temperature does not prove that the cooling system is distributing air correctly. Insufficient or unbalanced pressure may leave certain racks without enough cooling air.

Correct differential pressure measurement in a data centre provides evidence that cannot be obtained from a temperature meter or airflow meter alone.

What Does a Differential Pressure Meter Measure?

A differential pressure meter measures the difference between two pressure points.

It normally has two pressure connections:

• Positive or high-pressure port

• Negative or low-pressure port

The displayed result shows the pressure difference between the two connected locations.

Depending on the instrument, common units may include:

• Pa

• hPa

• mbar

• mmH₂O

• inH₂O

• psi

Use the unit required by the facility procedure or equipment manufacturer.

Why Measure Differential Pressure in a Data Centre?

Differential pressure testing may help evaluate:

• Raised-floor plenum pressure

• Server room versus corridor pressure

• Cold-aisle containment

• Hot-aisle containment

• Cooling-unit filter condition

• Airflow distribution

• Uncontrolled air leakage

• Cooling-zone imbalance

• Pressure changes after rack installation

• Pressure changes after moving floor tiles

The measurement should be interpreted together with temperature, airflow and equipment-load information.

Common Data Centre Pressure Problems

Possible problems include:

• Low raised-floor pressure

• Uneven pressure across the room

• Excessive open floor grilles

• Unsealed cable penetrations

• Missing floor panels

• Underfloor cable congestion

• Cooling-fan performance problems

• Dirty filters

• Open containment doors

• Damaged containment panels

• Incorrect room-pressure relationship

• Air leakage through doors or walls

Essential Inspection Tools

A complete cooling investigation may require:

• Differential pressure meter

• Airflow meter or anemometer

• Temperature and humidity meter

• Elitech RC-5 Temperature Data Logger

• Elitech GSP-6 Pro Temperature and Humidity Data Logger

• Noyafa NF-522 Thermal Camera

• Suitable pressure tubing

• Pitot tube where required

• Temperature probes

• Inspection and documentation tools

The correct accessory depends on the measurement location and purpose.

Differential Pressure Meter Versus Airflow Meter

For a full cooling assessment, technicians may require both instruments.

Differential Pressure Meter Versus Temperature Meter

Pressure may help explain why a rack is hot, but it does not replace direct temperature measurement.

Application 1: Raised-Floor Plenum Pressure

Raised-floor cooling systems use the underfloor space to distribute cooling air.

The pressure beneath the floor helps drive air through:

• Perforated floor tiles

• Cooling grilles

• Floor diffusers

• Approved rack openings

If pressure is too low or uneven, distant racks may receive insufficient cooling airflow.

How to Measure Raised-Floor Pressure

A typical measurement compares:

• High-pressure side: underfloor plenum

• Low-pressure side: server room

Follow the facility’s approved measurement method.

General process:

1. Inspect the meter and tubing.

2. Select the required unit.

3. Allow the meter to stabilise.

4. Zero the instrument.

5. Connect the pressure tubing correctly.

6. Position the pressure points consistently.

7. Avoid blocking or disturbing airflow.

8. Record the result.

9. Repeat at several locations.

10. Compare with the design or approved reference.

Only authorised personnel should open raised-floor panels.

Where Should Raised-Floor Measurements Be Taken?

Possible locations include:

• Near the cooling unit

• Centre of the room

• Farthest rack from cooling supply

• High-load rack area

• Problem rack

• Normal reference rack

• End of each cold aisle

• Area with previous low-airflow complaints

One measurement does not show how evenly pressure is distributed.

What Can Cause Low Raised-Floor Pressure?

Possible causes include:

• Open cable penetrations

• Missing floor panels

• Excessive number of open tiles

• Incorrect tile positions

• Underfloor obstructions

• Cooling-fan problem

• Air leakage

• Damaged floor system

• Incorrect damper position

• Reduced cooling-unit airflow

Do not increase fan speed or move floor tiles before identifying the cause.

What Can Cause Uneven Raised-Floor Pressure?

Possible causes include:

• Cable congestion

• Structural obstruction

• Poor floor-tile distribution

• Air leakage near cooling units

• Long airflow path

• Unbalanced cooling units

• Open floor penetrations

• Different aisle heat loads

Pressure mapping at several locations can help identify the pattern.

Application 2: Server Room Versus Corridor Pressure

A pressure difference may affect air movement through:

• Doors

• Door gaps

• Cable openings

• Wall penetrations

• Ceiling openings

An unsuitable pressure relationship may allow:

• Warm-air entry

• Humid-air entry

• Dust entry

• Loss of cooled air

• Door-operating difficulty

Measure according to the intended room-pressure design.

Do not assume that positive or negative pressure is always correct without checking the facility requirements.

How to Measure Room-to-Corridor Pressure

A typical comparison uses:

• One pressure point inside the server room

• One pressure point in the corridor

Record:

• Door position

• Cooling units operating

• Ventilation-system status

• Time

• Nearby door activity

• Measurement location

• Pressure unit

A door opening nearby can change the result significantly.

Application 3: Cold-Aisle Containment

Differential pressure measurement can support an investigation into whether cooling air is properly contained and supplied.

Check:

• Containment doors

• Roof panels

• Gaps around racks

• Missing blanking panels

• Floor tiles

• Cable penetrations

• Rack arrangement

Combine pressure readings with rack-inlet temperature and airflow measurements.

Application 4: Hot-Aisle Containment

Hot-aisle containment should direct equipment exhaust toward the cooling return path.

Pressure and airflow problems may cause hot air to escape into cold equipment intakes.

Possible signs include:

• Warm rack fronts

• Hot air near containment doors

• Uneven rack-top temperature

• Cooling units operating continuously

• Temperature alarms despite a cool room

Use thermal imaging to identify temperature patterns and data loggers to monitor changes over time.

Application 5: Cooling-Unit Filter Pressure Drop

A differential pressure meter may help compare pressure before and after a filter when the equipment design and access points allow it.

An increasing pressure difference may indicate:

• Dirty filter

• Blocked filter

• Incorrect filter

• Airflow restriction

• Installation problem

Interpret the reading according to the cooling-unit manufacturer’s recommendations.

Do not insert pressure tubing into operating equipment without suitable access points and authorisation.

Application 6: Air-Handling Equipment

Differential pressure testing may support inspection of:

• Filters

• Coils

• Fans

• Duct sections

• Dampers

• Air-handling units

The correct testing procedure depends on the equipment design.

Step 1: Inspect the Instrument

Before measurement, check:

• Battery

• Display

• Tubing

• Connectors

• Port condition

• Selected unit

• Measurement range

• Zero function

• Calibration status

Damaged or leaking tubing can cause incorrect results.

Step 2: Check the Tubing

Inspect for:

• Cracks

• Kinks

• Blockage

• Moisture

• Loose connection

• Incorrect size

• Excessive length

• Pinching

Keep the pressure tubes secure and away from moving equipment.

Step 3: Zero the Meter

Zero the instrument according to the manufacturer’s instructions.

Zeroing may be required:

• Before each measurement session

• After changing location

• After temperature changes

• After reconnecting tubing

• When the display does not return to zero

Do not zero the meter while a pressure difference is still applied.

Step 4: Connect the Correct Ports

Reversed tubing may produce a negative result.

Clearly identify:

• High-pressure point

• Low-pressure point

• Positive port

• Negative port

A negative reading is not automatically an instrument fault. It may show that the actual pressure direction is opposite to the assumed direction.

Step 5: Select the Correct Range and Unit

Use a meter capable of resolving the small pressure differences expected in ventilation and data-centre applications.

An excessively wide measurement range may provide inadequate resolution for low-pressure work.

Record the measurement unit with every reading.

Writing only “pressure = 5” is not sufficient.

Step 6: Keep Measurement Positions Consistent

For repeatable results, maintain:

• Same pressure-point position

• Same tube arrangement

• Same door condition

• Same cooling-unit status

• Same airflow condition

• Same measurement duration

Mark or document permanent reference points where appropriate.

Step 7: Allow the Reading to Stabilise

Pressure may fluctuate because of:

• Fan control

• Door movement

• Cooling cycles

• Equipment operation

• Nearby personnel

• Air turbulence

Observe the reading for a suitable period and record whether it is stable or fluctuating.

Step 8: Take Multiple Readings

Repeat the measurement and compare results.

For pressure mapping, use the same method at:

• Problem location

• Normal reference location

• Near cooling supply

• Far end of the room

• High-load zone

This provides more useful information than a single reading.

Step 9: Record Operating Conditions

Record:

• Cooling units operating

• Fan speed

• Door position

• Containment condition

• Floor-tile arrangement

• Rack load

• Maintenance activity

• Time

• Temperature and humidity

Pressure results cannot be compared reliably if operating conditions are different.

Step 10: Compare With Temperature and Airflow

A complete investigation might show:

Step 11: Use Data Loggers

Pressure readings are often taken as spot measurements.

Temperature loggers can show whether the suspected pressure or airflow problem causes:

• Overnight heating

• Repeated rack-top temperature rise

• Cooling-cycle variation

• Slow recovery after power events

Use:

• Elitech RC-5 for temperature trending

• Elitech GSP-6 Pro for temperature and humidity trending

Step 12: Use Thermal Imaging

The Noyafa NF-522 Thermal Camera may help identify:

• Hot rack fronts

• Escaping hot air

• Cooling imbalance

• Hot equipment

• Electrical hotspots

• Unusual surface-temperature patterns

Thermal imaging does not measure differential pressure or air velocity.

Example: Low Pressure at the End of One Aisle

Possible causes include:

• Underfloor cable obstruction

• Air leakage closer to the cooling unit

• Too many open tiles upstream

• Incorrect floor-grille distribution

• Long airflow path

• Insufficient fan output

Measure pressure and airflow at several points along the aisle.

Example: Pressure Is Normal but One Rack Is Hot

Check:

• Rack inlet airflow

• Blanking panels

• Cable congestion

• Equipment fans

• Equipment orientation

• Rack load

• Hot-air recirculation

• Local electrical hotspot

A normal underfloor pressure does not prove that cooling air passes through the rack correctly.

Example: Humidity Rises When the Door Opens

Check:

• Room-to-corridor pressure

• Door seals

• Adjacent-area humidity

• Ventilation balance

• Frequency and duration of door opening

Use the GSP-6 Pro to compare humidity changes with door activity.

Example: Cooling Filter Frequently Becomes Dirty

Measure the approved pressure drop across the filter and inspect:

• Filter type

• Installation direction

• Upstream contamination

• Air leakage around the filter

• Maintenance interval

• Fan operation

Use the manufacturer’s acceptance criteria.

Common Measurement Mistakes

Avoid:

• Reversing the positive and negative ports

• Using damaged pressure tubing

• Failing to zero the meter

• Recording no unit

• Measuring during inconsistent door conditions

• Taking only one reading

• Comparing readings from different locations

• Holding the tube in turbulent airflow incorrectly

• Ignoring cooling-unit status

• Treating pressure as airflow

• Assuming higher pressure is always better

• Changing floor-tile positions without assessment

• Failing to repeat testing after corrective work

What Should the Inspection Record Include?

Document:

• Date and time

• Meter model and identification

• Measurement unit

• High-pressure location

• Low-pressure location

• Exact test position

• Cooling equipment operating

• Fan condition

• Door position

• Containment condition

• Temperature and humidity

• Pressure result

• Airflow result

• Corrective action

• Verification result

Selecting a Differential Pressure Meter

Consider:

• Measurement range

• Resolution

• Accuracy

• Supported units

• Zeroing function

• Positive and negative pressure capability

• Data hold

• Minimum and maximum functions

• Data logging if required

• Tubing and accessories

• Calibration support

• Application environment

Select the meter according to the expected pressure range, not only the lowest price.

Recommended Data Centre Cooling Kit

A practical toolkit may include:

• Differential pressure meter

• Airflow meter

• Temperature and humidity meter

• Elitech RC-5

• Elitech GSP-6 Pro

• Noyafa NF-522 Thermal Camera

• Suitable pressure tubing

• Pitot tube where required

• Temperature probes

• Inspection records and labels

Verify Corrective Work

After correcting the suspected problem:

1. Repeat pressure measurements at the same points.

2. Use the same pressure unit.

3. Maintain comparable cooling conditions.

4. Repeat airflow checks.

5. Repeat rack-inlet temperature measurements.

6. Continue temperature logging.

7. Inspect containment and floor openings.

8. Compare with the original results.

9. Record the final condition.

Pressure Explains How Cooling Air Moves

Temperature identifies whether equipment is too warm.

Airflow measurement shows how much air is moving at a selected point.

Differential pressure helps explain what is driving that airflow and whether pressure relationships across the cooling system are correct.

Combining differential pressure, airflow, rack-inlet temperature, thermal imaging and continuous data logging provides stronger evidence for diagnosing uneven data-centre cooling.

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