Edgetech Instruments DewMaster Operating Manual
DewMaster
Chilled Mirror Hygrometer
OPERATORS MANUAL
19 Brigham Street ● Unit #8 ● Marlborough, MA USA 01752
Tel. [508] 263-5900 ● [800] 276-3729 ● Fax [508] 486-9348
E-mail h2o@edgetech.com ● www.edgetech.com
DewMaster
QUICK STARTUP GUIDE – Page 1
STARTUP
1. Connect the DewMaster to the AC Power Line.
2. If the Remote Mounting Kit was ordered, connect Dew Point Sensor Cable
to rear panel and to the Dew Point Sensor.
3. Connect Air Temperature Sensor to rear connector.
4. Install optional Pressure Sensor if required.
5. Wire Analog Outputs and Alarm Relay connections as needed.
6. Connect Serial Port if needed.
7. Install sampling system to Dew Point Sensor ports as needed.
8. Set rear panel Power Switch to ON position.
9. Wait for equilibration and SERVOLOCK indication on Display.
REPROGRAMMING A SETTING
1. Press ENT on Keypad to enter selection menu.
2. Using the UP and DOWN and LEFT and RIGHT arrow keys, scroll to the
desired location of the parameter to be changed.
3. Press ENT again to begin changing the setting. The selected parameter
will flash. Use left and right Arrow keys as required to scroll to the location
of the digit to be changed. Use the numerical keypad to input the change.
4. When programming is completed, press ENT to accept the new setting
and ESC to exit the menu. The KEEP CHANGES? screen will appear.
Press ENT to lock in the change, or ESC to discard the change and return
to the previously programmed value.
DewMaster
QUICK STARTUP GUIDE – Page 2
ROUTINE MAINTENANCE (See Maintenance Section)
MIRROR CLEANING
The Automatic Balance Cycle (ABC) greatly minimizes cleaning
requirements of the internal Chilled Mirror Sensor. Contaminants in the air
will gradually build up on the mirror, to the point where manual cleaning is
eventually required. Periods of 90 days between cleanings are typical,
depending on the air source. An indication of CLEAN MIRROR on the
Display, after an ABC Cycle, will tell the user when cleaning is needed.
Use cotton swabs and isopropyl alcohol for mirror cleaning. The manual
shows the mirror location inside the Sensor.
AIR FILTER ELEMENT REPLACEMENT
If a Sampling System is used with the Chilled Mirror Sensor, mirror
cleaning can be minimized by using an in-line air filter in the system.
Depending upon the quantity of contaminants in the incoming air, the Air
Filter element may have to be replaced after a substantial period of
operation. Remove the air filter cover, replace the filter with a new one,
and reassemble.
TABLE OF CONTENTS Page
1.0 Quick Startup Card (Removable)
2.0 List of Illustrations 4
3.0 Introduction 5
3.1 General Description 5
3.2 System Overview 5
3.3 Dew Point Sensor 6
3.4 Control Unit 6
3.5 Instrument Options 7
3.5.1 Measured Parameters 7
3.5.2 Analog Outputs 7
3.5.3 Alarm Relay 7
3.5.4 Pressure 7
3.6 Available Accessories 7
3.6.1 Remote Sensor Mounting Kit 7
3.6.2 Available Sample Line Filters 7
3.6.3 Sample Module Kit 7
4.0 Warranty Statement 8
5.0 Quality Statement 9
6.0 N.I.S.T. Traceability 10
7.0 Glossary 11
8.0 Installation 12
8.1 Unpacking 12
8.2 Control Unit Installation 12
8.2.1 Control Unit Placement 12
8.2.2 Wiring Connections 12
8.3 Sensor Setup for Accurate Dew Point Measurements 12
8.3.1 Sample Connections 12
8.3.2 Coolant Connections 13
8.3.3 Sampling Configurations 14
8.3.4 Preheating Sensor and Sample Lines 15
8.3.5 Selection of Components - Low Dew Points 16
8.3.6 Material Moisture Properties 16
8.3.7 Selection of Sample Pumps 17
8.3.8 Recommended Hardware 18
8.3.9 Pressure Measurements 18
8.4 Sources of Contamination 18
8.5 Sample Flow Rate 19
9.0 Basic Block Diagram Theory of Operation 21
9.1 Basic Block Diagram Description 22
10.0 Panel Description 23
10.1 Front Panel 23
10.2 Rear Panel 24
11.0 Information Display Functions 26
11.1 Information Displayed 26
12.0 Operating the DewMaster 28
12.1 Information Display 28
12.1.1 Time and Date 28
12.1.2 System Status 28
12.1.3 Main Displays 29
12.1.4 Bar Graph 29
12.2 Programming the DewMaster 29
12.2.1 Keypad Operation 29
12.2.2 Scroll Menu 30
12.2.3 Display Setup 30
12.2.4 Sample Averaging 31
12.2.5 Analog Output 31
12.2.6 ABC Cycle 32
12.2.7 Alarm Relay 32
12.3 Programming the Serial Port 33
12.3.1 Serial Output 33
12.3.2 External Device Connections 33
12.3.3 PC or Terminal Setup 33
12.3.4 RS-232 Commands and Parameters 33
13.0 The Chilled Mirror Dew Point Sensor 39
13.1 Theory of Operation 39
13.2 Mirror Automatic Balance Cycle (ABC) 40
13.3 Care and Maintenance of the Chilled Mirror Sensor 41
14.0 Maintenance 42
14.1 Routine Maintenance 42
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14.2 Mirror Cleaning Schedule 42
14.3 Mirror Cleaning 43
14.4 Understanding ABC and Mirror Messages 43
14.5 Sensor PRT Calibration Check 44
14.5.1 Performing the PRT Calibration Check 44
14.6 Servo Gain Adjustment 44
14.7 Display Contrast Adjustment 45
14.8 Replacing the Fuse 45
14.9 Air Filter Replacement (if used) 45
14.10 Modifying the Analog Outputs 46
15.0 Specifications 47
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2.0 LIST OF ILLUSTRATIONS Page
3-1 DewMaster Chilled Mirror Dew Point Hygrometer 5
8-1 Typical Sampling System 16
8-2 Typical Sample Line Material Characteristics 17
8-3 Flow Corrections for Various Pressures 20
8-4 Flow Corrections for Various Gases 20
9-1 Basic Block Diagram 21
10-1 DewMaster Front Panel 23
10-2 DewMaster Rear Panel 24
11-1 The Information Display 26
12-1 Keypad 30
12-2 Programming the Current Date 31
12-3 Setting the Analog Output Range 31
12-4 Programming the Alarm Relay Setpoint 32
12-5 Locking In the Programming Changes 32
13-1 Chilled Mirror Block Diagram 39
14-1 Cleaning the Mirror 43
14-2 Replacing the Fuse 45
14-3 Analog Mode Switches 46
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3.0 INTRODUCTION
3.1 GENERAL DESCRIPTION
The DewMaster Dew Point Hygrometer (Figure 3-1) is a microprocessor
based, programmable humidity measurement instrument with many
microprocessor controlled features built-in.
Using the highly accurate Optical Chilled Mirror (OCM), primary dew point
measurement technique, the DewMaster was developed for process control
and continuous unattended operation as well as laboratory and research
applications. Three sensors are available, with a depression of either 45°C
(S1 Sensor), 65°C (S2 Sensor), or 95° (S3 Sensor) from an ambient
temperature of 25°C. The system can measure frost points as low as -75°C
(1 PPMv) with the S3 Sensor and auxiliary cooling.
Figure 3-1. DewMaster Chilled Mirror Dew Point Hygrometer
3.2 SYSTEM OVERVIEW
The basic DewMaster system consists of a Control Unit and the S1, S2, or S3
Dew Point Sensor. The Control Unit has a menu driven LCD graphics
display, parameter averaging, Automatic Balance Cycle (ABC), one analog
output, one alarm relay and a RS232C serial port.
Optional features include an Ambient Temperature Probe, three Analog
Outputs, two Form C Alarm Relays, and a live pressure input. The backlit
LCD can display up to three user-selected parameters simultaneously.
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Available readout parameters include Dew Point (C or F), Ambient
Temperature (C or F), PPMv, Wet Bulb, Grains/lb, and Pressure in PSI. All
measured, as well as all calculated values can be displayed as a rolling
average from one to sixteen samples at a one sample-per-second rate. A
hierarchical menu structure driven by “soft keys” provides a user-friendly
method of choosing display options and setting limits and functions from the
front panel.
The Automatic Balance Cycle (ABC) can be set to calibrate the sensor optics
at preset times and intervals or can be initiated manually at any time.
Each analog output is available on the rear panel as 0 to 5 VDC or 4 to 20 mA
and can be set to follow any parameter with individually adjustable high and
low limits. The outputs can be set to TRACK the Dew Point temperature
during the ABC cycle or HOLD the last value prior to the ABC cycle.
The half duplex configured RS232C serial port can be used to set up
functions, control the operation, and output data to a data-recording device.
3.3 DEW POINT SENSOR
The Dew Point sensor has a chromium plated mirror to provide superior
corrosion and abrasion resistance. The sensor is normally mounted on the
instrument rear panel, but it can be mounted remotely up to 75 meters (250
feet) from the instrument by using the optional Remote Cable Mount kit.
Each sensor is equipped with a built-in cooling jacket to extend the
measurement range to lower dew/frost points. The S2 Sensor has a
depression range of 65°C (117°F) at a base temperature of 25°C and the S1
Sensor has a depression of 45° C (81°F). The S3 Sensor has a depression of
95°C (171°F) and comes equipped with two cooling fans in addition to the
cooling jacket. The response time is as high as 1.5°C (2.7°F) per second at
dew points above 0° Celsius. A spin-off cover permits easy access to the
mirror for cleaning without the need of tools or disconnecting sample lines.
3.4 CONTROL UNIT
The DewMaster Control Unit operates entirely under microprocessor control.
State-of-the-art software provides the opportunity to include a flexible,
informational, and user friendly interface. The Information Display and the
Keypad are the only items on the front panel. Setup and operation of the
Control Unit can be programmed via the front panel keypad or the RS-232
serial port.
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3.5 INSTRUMENT OPTIONS
3.5.1 Measured Parameters
The basic unit measures Dew Point. Optional parameters include Ambient
Temperature, RH, PPMV, Gr/lb, and Wetbulb. Consult the factory for
additional parameters.
3.5.2 Analog Outputs
Two additional outputs, for a total of three programmable, 0 - 5 VDC or 4 - 20
mA channels. See the Maintenance section for a description of the internal
programming switches to change from voltage to current outputs.
3.5.3
Alarm Relay
A second relay option provides an additional Form C (SPDT) relay which can
be independently set for a high or low limit on any measured parameter.
When an alarm condition occurs, the relay activates and a flashing message
appears on the display also. The alarm conditions can be set up via the front
panel or the RS232 serial port.
3.5.4 Pressure
The live pressure sensor option enables the measurement of pressuredependent variables such as PPMV or GR/lb. Standard ranges are 0 - 25
PSIA and 0 -100 PSIA. Consult the Factory for the measurement of other
pressure-dependent variables.
3.6 AVAILABLE ACCESSORIES
3.6.1 Remote Sensor Mounting Kit
When it is required to locate the sensor remotely from the control unit, the
optional Remote Mounting Kit must be used. This kit consists of the mounting
hardware, connectors, and cable necessary for locating the sensor remotely.
The standard cable length is 10 ft., however, optional custom lengths up to 75
meters (250 feet) can be ordered.
3.6.2 Available Sample Line Filters
In-line Sample Filter
In-line Coalescing Filter
3.6.3 Sample Module Kit
The Sample Module Kit consists of a free piston vacuum pump and a variable
area flow meter, housed within a NEMA-4X enclosure. The pump can be
supplied to operate on either 115 VAC or 230 VAC ±10%, 50 to 60 Hz input
power.
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4.0 WARRANTY STATEMENT
All equipment manufactured by EdgeTech is warranted against defective
components and workmanship for repair at their plant in Massachusetts,
free of charge, for a period of twelve months. Malfunction due to
improper use is not covered in this warranty and EdgeTech disclaims
any liability for consequential damage resulting from defects in the
performance of the equipment. No product is warranted as being fit for a
particular purpose and there is no warranty of merchantability. This
warranty applies only if (i) the items are used solely under the operating
conditions and in the manner recommended in the instruction manual,
specifications, or other literature; (ii) the items have not been misused or
abused in any manner or repairs attempted thereon; (iii) written notice of
the failure within the warranty period is forwarded to EdgeTech and the
directions received for properly identifying items returned under warranty
are followed; and (iv) the return notice authorizes EdgeTech to examine
and disassemble returned products to the extent EdgeTech deems
necessary to ascertain the cause for failure. The warranties expressed
here are exclusive. There are no other warranties, either expressed or
implied, beyond those set forth here, and EdgeTech does not assume
any other obligation or liability in connection with the sale or use of these
products.
Equipment not manufactured by EdgeTech is supported only to the
extent of the original manufacturer’s warranties
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5.0 EDGETECH’S COMMITMENT TO QUALITY
Thank you for purchasing one of our products. At EdgeTech, it is our
policy to provide cost-effective products and support services that
meet or exceed you requirements, to deliver them on time, and to
continuously look for ways to improve both. We all take great pride in
the products we manufacture.
We want you to be entirely satisfied with your instrument. The
information contained in this manual will get you started. It tells you
what you need to get your equipment up and running, and introduces
its many features.
We always enjoy hearing from the people who use our products. Your
experience with our products is an invaluable source of information
that we can use to continuously improve what we manufacture. We
encourage you to contact or visit us to discuss any issues whatsoever
that relate to our products or your application.
The Employees of EdgeTech
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6.0 N.I.S.T. TRACEABILITY – WHAT DOES IT MEAN?
The DewMaster is certified by Edgetech to be traceable to N.I.S.T., the National
Institute of Standards and Technology (formerly known as the National Bureau of
Standards, or NBS), in Gaithersburg, Maryland, U.S.A. You have received a
Certificate of Calibration with this instrument. What does N.I.S.T. Traceability
mean in terms of this instrument?
The DewMaster measures Dew Point using the Optical Chilled Mirror (OCM)
technique, which provides a primary rather then a secondary measurement of
Dew Point temperature. In addition, Dew Point is a fundamental measurement of
humidity. It is not affected by temperature.
Both the Dew Point temperature and the Air Temperature are measured using
Platinum Resistance Thermometers (PRTs). These devices are coils of nearly
pure platinum, where the rate of change of resistance with temperature is
precisely known. Resistance is accurately measured and is automatically
converted to temperature information within the instrument.
Other parameters, such as Percent Relative Humidity, PPMv, Gr/lb, and Wet
Bulb temperature, are microprocessor-calculated from the directly measured
Dew Point, Temperature, and Pressure (optional) information.
TRACEABILITY:
• 1. The precise platinum resistance thermometers are N.I.S.T. traceable
by the traceable resistance standards maintained by the PRT
manufacturers.
• 2. A multi-point Dew Point calibration is performed on every chilled
mirror sensor, using EdgeTech’s traceable secondary dew point
standard. This instrument, a precise chilled mirror hygrometer, is
periodically sent directly to N.I.S.T. for certification against the USA’s
Dew Point transfer standard, a Two-Pressure Generator.
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7.0 GLOSSARY
ABC: Automatic Balance Control – a method of maintaining accuracy in
the presence of contamination and minimizing maintenance
requirements.
Analog Out A voltage or current that tracks changes in a measured parameter.
AT Air Temperature or Ambient Temperature
Depression The magnitude of available mirror cooling in the chilled mirror
sensor.
DP Dew Point Temperature – the temperature that moisture in the
air just begins to condense on a cooled surface.
Hold Analog output which holds the last humidity reading just before the
ABC cycle.
Hysteresis The tendency of a sensor to give one set of readings when going
up, and a different set of reading when going down.
Mirror A small metallic reflective surface within the dew point sensor.
RH Percent Relative Humidity – the ratio between the actual moisture
content in the chamber and the maximum moisture content if the
chamber air was saturated, at a given air temperature.
RS-232 An accepted industry standard for a serial digital interface.
Serial Port See RS-232.
Servolock
Slew Rate The rate of temperature change of the mirror assembly in the
Track Analog output which follows (tracks) the mirror temperature during
TM
A method of indicating that the system is locked on and tracking the
dew point.
chilled mirror dew point sensor.
the ABC cycle.
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8.0 INSTALLATION
8.1 UNPACKING
Remove the DewMaster Dew Point Hygrometer from its shipping carton and
remove any shipping ties, clamps, and packing material. Save the Certificate
of Calibration shipped with this manual. Locate and save the small box
containing the Cleaner Kit included in the shipping carton. The Model S1, S2
or S3 sensor is normally attached to the DewMaster Control Unit, except
when the optional Remote Mounting Kit is ordered.
8.2 CONTROL UNIT INSTALLATION
8.2.1 CONTROL UNIT PLACEMENT
Install the DewMaster in locations where the ambient temperature will not
exceed the specified ambient temperature range.
Sensors are often specified to have a wider temperature operating range than
the control unit. When the anticipated operating range of the sensor is
expected to be outside the operating temperature range of the instrument, the
sensor should be removed from the instrument and mounted remotely by
means of the optional Remote Mounting Kit.
Always maintain the sensor temperature at least 5°C above the dew point
temperature of the gas being measured. This prevents unwanted
condensation on the inside of the sensor body. In addition, it supports proper
operation of the heat pump control circuit.
8.2.2 WIRING CONNECTIONS
Connect the DewMaster control unit to a grounded, instrument quality power
source of between 95 to 240 VAC, 50 - 60 Hz.
Note: See correct power line fuse values in Specifications section.
You may wish to wire the Analog Output and Alarm Relay connectors.
Connection information is clearly shown on the rear panel of the DewMaster.
Specifications for the Serial Port, and also the Alarm Relay contact ratings,
are in the Specifications section.
8.3 SENSOR SETUP FOR ACCURATE DEW POINT
MEASUREMENTS
8.3.1 SAMPLE CONNECTIONS
A basic requirement of accurate dew point measurements is the proper
design of the gas sampling system. In order to measure the moisture content
of a gas, the sampling system design must consider the effects of the
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materials used, the sample pressure and flow rate, the range of dew points to
be measured, and ambient conditions.
Generally, for dew point temperatures above -18°C, the selection of sample
line materials is not critical. It is only necessary to ensure that the temperature
and pressure ratings are adequate to handle the sample, and that the
connections are gas tight. For dew point temperatures below -18°C, some
attention must be given to the selection of materials in the sample system.
Tubing material, for example, should be hydrophobic in nature, such as
copper or stainless steel. Refer to subsection 8.3.5, Selection of
Components.
Dew point is a measurement of the partial pressure of water vapor in a gas.
Increasing the total pressure of the gas increases the partial pressure of each
of its constituents, raising the dew point. See subsection 8.3.9, Pressure
Measurements.
It is essential that the temperature of sampling components not be allowed to
drop below the dew point temperature of the sample. This prevents
condensation from occurring within the line, causing an erroneous
measurement. Sampling lines and the sensor must be properly preheated
when measuring dew points above ambient temperature. Refer to Preheating
Sensor and Sample Lines, subsection 8.3.4.
In general, the most common problem areas that affect the moisture
measurement of a sampled gas are:
1. Length of the process and/or sample lines.
2. Leaks in the process and/or sample lines.
3. Adsorption or absorption of moisture in the process and sample lines
due to the materials.
4. Excessive elbows, tees, valves, or other fittings used in the sample
lines.
5. Back diffusion of moisture into a pressurized system, particularly at low
dew/frost points.
6. Condensation within the process line and sample line at high dew
points.
7. Diffusion through the sampling materials.
The procedures and parts recommended in this manual should be used only
as a guide in selecting and designing sampling systems. For special or
unique applications, contact an EdgeTech Application Engineer for assistance
in selecting sampling components.
8.3.2 COOLANT CONNECTIONS
For most applications, the Model S1, S2 or S3 sensor does not need cooling
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