Dew Point Temperature Measurement of Compressed Air

Optimizing Compressed Air Systems with Vaisala Measurement Solutions

Compressed air reliability depends heavily on dryness. When moisture is not controlled, common outcomes include corrosion in distribution piping, sticking pneumatic valves, unstable instrumentation air, product defects (painting/powder processes), and freeze-ups in outdoor networks. The most direct way to control dryness is to measure and trend pressure dew point (PDP) at the right points in the system.

Vaisala offers a dedicated product range purpose-built for low-humidity compressed air, pressurized lines, and long-term stability, making it suitable for both continuous monitoring and maintenance diagnostics.

What to measure: pressure dew point (PDP)

In compressed air applications, dew point is typically managed as pressure dew point—the temperature at which water begins to condense at line pressure. PDP trending helps you:

• Confirm dryer performance (refrigerant or desiccant)
• Detect moisture carryover and “water spike” events
• Identify gradual dryer drift before downtime occurs
• Avoid over-drying (energy optimization)
• Validate air quality at critical points of use

Vaisala’s compressed-air dew point measurement range (how to choose)

1) Continuous inline monitoring in pressurized pipelines (main headers / ring mains)

Best when you want permanent, high-confidence trending in the compressor room or at key branches.

• Use a pipeline-rated dew point & temperature probe designed for low humidity and pressurized compressed air.
• Integrate via an industrial transmitter platform for analog outputs, digital comms, and alarms.

Typical placement: after the dryer + final filtration, and at least one downstream “worst-case” point.

2) Compact transmitters for dryers and OEM skids (small footprint)

Best for refrigerant dryers, small desiccant dryers, packaged skids, and point-of-use dryer verification.

• Compact dew point transmitters are easy to integrate into OEM panels.
• Ideal where space is limited and you need a simple, stable dew point signal.

Typical placement: dryer outlet to confirm performance, or point-of-use where moisture sensitivity is high.

3) Plant-wide standardization with a modular transmitter ecosystem

Best when you want a uniform approach across multiple locations (compressor room, distribution, and critical points of use).

• Use a common transmitter family to standardize wiring, outputs, configuration, and maintenance practices.
• This reduces spares complexity and accelerates commissioning across sites.

4) Portable verification and troubleshooting (maintenance, commissioning, QA)

Best for audits, commissioning, fault isolation, and cross-checking multiple points without permanent installation.

• A handheld indicator/data-logger with compatible probes enables quick comparisons:
• Dryer outlet vs. point-of-use
• Different branches across the ring main
• Suspected “wet air” complaint areas

5) Sampling accessories for harsh real-world compressed air conditions

Even with high-quality sensors, installation drives reliability. Sampling and protective accessories are recommended when your system has:

• Frequent drain issues or suspected water slugs
• Oil aerosols or contamination risk
• Difficult access locations where safe servicing is required

Sampling also improves repeatability by providing controlled flow conditions at the sensor.

Best-practice installation (compressed air specific)

• Measure where it matters: at dryer outlet (performance) + point-of-use (process protection).
• Avoid dead legs: stagnant sections can show misleading dew point values.
• Protect against water spikes: ensure drains work; use sampling where carryover is possible.
• Design for maintenance: isolation valves and service-friendly mounting reduce downtime.
• Trend in SCADA/PLC: trends reveal slow dryer drift and seasonal effects long before failures.

Recommended Vaisala part numbers (models + common accessories)

A) Permanent inline monitoring (pressurized lines)

• DMP8 — Dew Point & Temperature Probe (for low-humidity industrial applications, suitable for pressurized pipelines)

Transmitter / integration (choose based on output needs):

• Indigo201 — Analog output transmitter platform
• Indigo202 — RS-485 / Modbus RTU transmitter platform

Power accessory (when required):

• INDIGOPOWER24VSP — Mains power supply accessory for Indigo transmitters

B) Dryers, OEM skids, and compact installations

• DMT143 — Miniature Dew Point Transmitter (compressed air dryers / OEM)
• DMT143L — Miniature Dew Point Transmitter (variant for specific mechanical installation needs)

Common spares/accessories (useful for service readiness):

• HM47453SP — Stainless steel filter (DMT143/DMT143L)
• DRW010335SP — Sintered filter (DMT143)
• DM240FASP — Installation flange (ISO 1/2)

C) Portable commissioning, diagnostics, and spot checks

• INDIGO80 — Handheld Indicator / Data Logger

Common handheld-related accessories:

• 272075SP — Probe connection cable (M12–M12), 1.5 m
• CBL210493SP — Flat probe connection cable, 1 m
• 262195SP — M12–M8 cable (for connecting certain miniature transmitters to Indigo80)

D) Sampling (recommended where water spikes/contamination risk exists)

• DMT242SC — Sampling cell (threaded connectors)
• DMT242SC2 — Sampling cell (tube fitting style)

Note: Final ordering codes/configurations can vary by measurement range, output type, display option, cable/connector selection, and mounting hardware. For a clean BOM, it’s best to standardize on one or two architectures (inline header + compact dryer transmitter + portable kit) and then configure each measurement point consistently.

How General Tech Services can help?

General Tech Services can support specification and standardization of Vaisala dew point measurement across compressor rooms, dryers, and critical point-of-use locations—covering selection, installation approach (inline vs sampling), and PLC/SCADA integration.