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DPH-2020TP Industrial Dew Point Hygrometer with Temperature and Pressure Channels

General Description

The DPH-2020 is a two stage dew point hygrometer using the chilled mirror principle to determine the absolute humidity of a gas in terms of its dew- or frost-point temperature. It was specifically designed for critical industrial process applications. A state-of-the-art digital control system maintains the sensor mirror at the equilibrium point-- the point where a dew or frost layer is established on the mirror surface. A platinum resistance thermometer monitors the mirror temperature, which represents the dew- or frost-point temperature. Depending on the actual dew point, settling time from ambient may take a few seconds to one minute. Frost point measurements to –60° C or lower can be made. The high temperature Model DPH-2012 can make dew point measurements up to +120° C.



Rugged stainless steel sheeted mirror provides extra durability in industrial applications

Convenient front panel digital readout

Multi-stage/extend operating range

Both analog and RS-232 serial outputs

Two alarm limit relays for control use


Chilled mirror dew point hygrometers are used in a wide variety of industrial process-control and laboratory applications to ensure product quality, including:

Real time process control for pharmaceutical, painting, plate glass, paper, and injection-molding production

Production monitoring for dried foods and dry snack processing

Monitoring of storage environments and special purpose rooms such as museums, warehouses, computer and clean rooms

Manufacturing quality control for fabrication of sensitive electronic components such as semiconductors

Building HVAC or air quality monitoring

Heat treating furnace controls

Sensor can be remotely located from electronics enclosure

For very low dew point temperature applications, an integral chilled coolant loop can be used to extend the lower measurement limit of the system.



DPH-2020/2012 Dew Point Hygrometer

Mechanical Configuration

The DPH requires a sample stream of air or gas. The sample enters and exits the sensor via 1/8 National Pipe Thread (NPT) ports. Flow rates should be maintained between 0.2 and 1.0 standard cubic feet per hour (SCFH). The sensor operates between temperatures of –60° C to +80° C. A front panel DPM indicates the current dew point temperature to the user and set point relay contacts are provided. A Windows application supports remote viewing or integration with SCADA systems. The DPH-2020 can run from AC line or 12Vdc battery power; the DPH-2012 requires AC power.


Unlike other sensors (polymer or aluminum oxide) that must be discarded once contaminated, a chilled mirror hygrometer can easily be cleaned to restore its performance. To restore proper operation of the sensor, the measurement chamber can be easily opened, inspected, and cleaned. A mirror microscope provides a means of inspecting the condition of the mirror prior to opening. The top of the sensor hinges open easily without tools via a single finger-operated spring clip. The cleanliness of the sample gas governs how often the mirror will need to be cleaned, but it is typically an interval from days-to-months.

Compare these features we offer at no extra cost:


DPH sensor cross-section view



DPH sensor showing access to mirror for cleaning


DPH sensor rear view


DPH sensor bottom view of heat sink and integrated cooling fan

Mechanical Interface

Side view - dimensions in inches [cm]

Top view - dimensions in inches [cm]



Dew/frost point


2020: 65° C depression; from room ambient temperature of 22° C, dew/frost point measurements can be made to approx. -40° C with room temperature installations;


2012: +120° C to –40° C; down to –60° C with customer-supplied –20° C liquid coolant loop




± 0.1° C




± 0.01° C




± 0.01° C






Response time


35 seconds (typical)


Power Supply


2020: 110/220 Vac or 12Vdc
2012: 110/220 Vac only
approximately 100 watts


Gas contacts


Anodized aluminum, Viton, stainless steel, glass


Output signals


± 5 Vdc analog,
limit (Form C relay), RS-232


Storage Temp Range *


Sensor: -50° C to +80° C
Electronics: -50° C to +50° C

*Note: working depression limit is a function of ambient sensor temperature. A customer-supplied chilled coolant loop permits lower dew point range.


      Measurement span of one-and two-stages



Standard Accessories Provided at No Extra Charge



Totally inert mirror sensor chamber

Full digital control for precise operation

Analog and digital outputs, PLUS alarm relays

Mirror microscope permits visual verification of dew layer and mirror state during operation 

Forced air cooling improves reliability

Auxiliary liquid cooling loop permits even lower temperature depression operation

Chilled mirror principle of operation