COMET dew point sensors and transmitters for compressed air lines, cleanrooms, server rooms, HVAC ducts and cold storage. Every unit measures temperature and relative humidity and reports dew point directly – alongside absolute humidity, mixing ratio and specific enthalpy – over Ethernet, PoE, WiFi, RS485, RS232, 4-20 mA or 0-10 V. Need a handheld instead? See our dew point meters and hygrometers. Full buyer’s guide below the range.
COMET dew point sensors and transmitters for compressed air lines, cleanrooms, server rooms,...
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Temperature, RH, Counted values (dew point…) tr…
Temperature, RH, CO2, Dew point
Temperature, CO2, RH, Dew point
Temperature, Relative Humidity, CO2
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Thermometer Hygrometer with Ethernet interface an…
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Dew point is the temperature at which the air or gas being measured becomes saturated and water begins to condense. It is the number that tells you whether condensation will form on a cold surface, whether a compressed air line will hold water, and whether a controlled space is genuinely dry – questions relative humidity alone cannot answer, because the same 45% RH means something completely different at 5 degC than at 30 degC.
Every COMET instrument in this range measures temperature and relative humidity with a stable polymer sensor, then derives dew point from the pair. The same calculation also gives you absolute humidity, specific humidity, mixing ratio and specific enthalpy – COMET calls these the ‘counted values’ – and all of them are available on the display, over the digital interface and in the logged record.
Compressed air. The ‘P’ models – T3111P, T0211P, T3511P and H3531P – take a probe directly into a pressurised line at up to 25 bar and report pressure dew point across a -60 to +80 degC range, so you can verify that a refrigerant dryer is doing its job before moisture reaches tooling, instruments or product.
Cleanrooms and pharmaceutical storage. Ethernet and PoE models such as the T3510, T3511 and T3611 sit on the building network and expose dew point over SNMP, Modbus TCP and a web interface, with a traceable calibration certificate in the box.
Server rooms and data halls. Dew point, not RH, is the number that predicts condensation on chilled surfaces. The H3530 and H3531 add two relay outputs so an alarm can be raised – or a dehumidifier started – on a dew point setpoint rather than an RH one.
HVAC ducts and plant. Duct-mount models across every output type (T3113D, T3117, T0213D, T3413D, T7613D) drop into a duct on a stem and feed dew point back to the BMS as 4-20 mA, 0-10 V, RS485 or Ethernet. Cold storage and warehouses. WiFi models (W3710, W3711, W3721, W3745) report to COMET Cloud with no cabling, which suits racking and chambers where running a cable is the expensive part.
| Output | Models in this range | Typical use |
|---|---|---|
| 4–20 mA | T3111P, T3113D, T3117, T3110Ex, T3111Ex, T3113Ex | PLC and DCS analogue inputs. The Ex models are intrinsically safe for hazardous areas. |
| 0–10 V | T0211, T0211P, T0213, T0213D | Building management systems and HVAC controllers. |
| Ethernet | T3510, T3511, T3511P, T6540, T6541, T6545, H3530, H3531, H3531P, H3531R, H6520, H7530, H7531, T7510, T7511 | SNMP, Modbus TCP and a browser interface, on your existing LAN. |
| PoE | T3610, T3611, T6641, T7610, T7611, T7613D | One cable for data and power — no local supply needed at the sensor. |
| Wi‑Fi | W3710, W3711, W3721, W3745, W4710, W7710 | Reporting to COMET Cloud with no cabling to the measurement point. |
| RS485 / Modbus RTU | T3411, T3413D, T3419, T6440, T6445, T7410, H3430, H3431, H6420, H7430 | Multi-drop runs into a PLC or SCADA head end. |
| RS232 | T3311, T3313, T3319, T6340, T7310, H3331, H6320 | Direct connection to a single host. |
These are humidity-derived dew point instruments: they measure temperature and relative humidity with a polymer element and calculate dew point from the pair. COMET publishes the accuracy that results, and it is worth reading before you specify:
±-1.5 degC at a dew point of +10 degC and above
±2.0 degC at a dew point of 0 degC
±3.0 degC at a dew point of -10 degC
±6.0 degC at a dew point of -20 degC
That makes them well suited to condensation-risk monitoring and to compressed air downstream of a refrigerant dryer, where pressure dew point normally sits between +3 and +10 degC – the band where these instruments are at their most accurate.
They are not the right instrument for a desiccant dryer running at -40 degC or -70 degC pressure dew point, or for trace-moisture work in process gases. At those levels a chilled-mirror or metal-oxide instrument is the correct technology. If that is what you are measuring, call us on 1300 662 720 and we will point you to it rather than sell you the wrong thing.
Nor are these handheld instruments. Every product on this page mounts in a duct, a panel, an enclosure or a pressurised line and reports continuously. If you need to walk up to a line and take a reading, see our handheld dew point meters and hygrometers.
And they are not surface dew point gauges for protective-coating inspection. If you need to check whether steel is safe to paint, you are looking for a coating inspection DPM, which we do not stock.
A dew point sensor reports the temperature at which the air or gas it is measuring would become saturated and start to condense. The instruments in this range do it by measuring temperature and relative humidity with a polymer sensing element and calculating dew point from the two, which is the standard method for ambient and refrigerant-dried compressed air. Dedicated low-dew-point instruments use a chilled mirror or a metal-oxide element instead, which extends the range far lower at considerably higher cost.
For continuous monitoring - which is what this range covers - a fixed sensor or transmitter that feeds dew point to a PLC, BMS or network: 4-20 mA and 0-10 V for analogue inputs, RS485 or RS232 for serial,
Ethernet, PoE or WiFi for networked monitoring, logging and alarms.
For a walk-up spot check rather than a permanent installation, you want a handheld dew point meter instead - see our hygrometers and handheld meters.
Yes. The 'P' models - T3111P, T0211P, T3511P and H3531P - are built for it, with a probe rated for direct installation in a pressurised line at up to 25 bar, reporting pressure dew point rather than atmospheric dew point.
They suit systems dried by a refrigerant dryer, where pressure dew point normally sits between +3 and +10 degC - the band where their accuracy is best. For a desiccant dryer running at -40 degC or lower, you need a chilled-mirror or metal-oxide instrument instead - call us and we will point you to one.
The compressed-air models measure dew point from -60 to +80 degC with 0.1 degC resolution. Accuracy is graded by how dry the air is: +/-1.5 degC at a dew point of +10 degC and above, +/-2.0 degC at 0 degC,
+/-3.0 degC at -10 degC and +/-6.0 degC at -20 degC.
That is why we recommend them for refrigerant-dried compressed air and condensation-risk monitoring, and recommend a dedicated low-dew-point instrument below about -20 degC.
Relative humidity tells you how close the air is to saturation at its current temperature, so the same RH reading means different things at different temperatures. Dew point is an absolute figure: it tells you the actual temperature at which condensation will form, regardless of how warm or cold the space is. That is why dew point is the number that matters for condensation risk in a server room, for moisture carryover in a compressed air line, and for verifying that a controlled space is genuinely dry rather than merely warm.
Both. The H-series models (H3530, H3531, H3531P, H3531R, H3430, H3431) carry relay outputs that can be set to switch on a dew point threshold, so they can raise an alarm or start a dehumidifier directly. For an analogue signal, the T3111P transmits dew point as 4-20 mA and the T0211P as 0-10 V, both from compressed air at up to 25 bar.
A dew point sensor or transmitter is installed permanently - in a duct, a panel, an enclosure or a pressurised line - and reports continuously to a PLC, BMS, network or logging system. That is what this page lists.
A dew point meter is a handheld instrument you carry to the measurement point and read on the spot, typically for commissioning, spot checks and fault-finding rather than permanent monitoring. Those are on our hygrometers and handheld meters page.
