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 [e-mail] ● 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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3.0INTRODUCTION

3.1GENERAL 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.

3.6.2Available Sample Line Filters

In-line Sample Filter

In-line Coalescing Filter

3.6.3Sample 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.
ServolockTM	A method of indicating that the system is locked on and tracking the
	dew point.
Slew Rate	The rate of temperature change of the mirror assembly in the
	chilled mirror dew point sensor.
Track	Analog output which follows (tracks) the mirror temperature during
	the ABC cycle.

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8.0INSTALLATION

8.1UNPACKING

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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