Edgetech RH CAL Operator's Manual

RH CAL

Relative Humidity Calibrator

OPERATORS MANUAL

E-mail [e-mail] ● www.edgetechinstruments .com

Rev. A March 2011

399 River Road ● Hudson, MA USA 01749

Tel. [508] 263-5900 ● [800] 276-3729 ● Fax [508] 486-9348

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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 Operating Controls 6

4.0 Warranty Information 8

5.0 Edgetech Instruments Inc.’s Commitment to Quality 9

6.0 N.I.S.T. Traceability – What does It Mean? 10

7.0 Glossary 11

8.0 Installation 12

8.1 Unpacking 12

8.2 Wiring Connections 12

8.3 Water Fill 13

8.4 Air Connection (Optional) 13

9.0 Basic Block Diagram Theory of Operation 14

9.1 Basic Block Diagram Description 15

10.0 Panel Description 16

11.0 Information Display Functions 18

11.1 Information Displayed 18

12.0 Operating the RH Calibrator 20

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12.1 System Status 20

12.2 Keypad Operation 21

12.3 Programming the RH-CAL 22

12.4 Calibrating RH Sensors 25

12.5 RS-232 Serial Port Setup 26

13.0 The Chilled Mirror Dew Point Sensor 30

13.1 Theory of Operation 30

13.2 Automatic Balance Cycle 31

13.3 Care and Maintenance of the Sensor 32

14.0 Maintenance 33

14.1 Routine Maintenance 33

14.1.1 Mirror Cleaning Schedule 33

14.1.2 Cleaning the Mirror 33

14.1.3 Dryer Tube Maintenance 34

14.1.4 Filling the Saturator 35

14.1.5 Removing the Front Panel 35

14.2 Replacing the Fuse 36

14.3 Modifying the Analog Output 36

15.0 Specifications 38

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2.0 LIST OF ILLUSTRATIONS Page

3-1 RH Calibrator Panel 5
8-1 Removing Shipping Plug 12
8-2 Filling the Saturator 13
9-1 Basic Block Diagram 14
10-1 Panel Description 16
11-1 The Information Display 18
12-1 Keypad 21
12-2 Changing the RH Setpoint 22
12-3 Changing the AT Setpoint 22
12-4 Selecting Dew or Frost 24
12-5 Locking In the Changes 25
13-1 Chilled Mirror Block Diagram 30
14-1 Cleaning the Mirror 33
14-2 Replacing the Dryer Material 34
14-3 Fuse Location 36
14-4 Analog Mode Switch 36
14-5 DIP Switch Configuration 37

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3.0 INTRODUCTION

3.1 GENERAL DESCRIPTION

The RH CALIBRATOR is a microprocessor based, programmable humidity control
and measurement instrument with many microprocessor controlled features built-in.

Using the NIST Traceable Optical Chilled Mirror primary measurement technique,
the RH CALIBRATOR was developed for precise calibration of RH Sensors and
Transmitters, as well as laboratory and research applications.

3.2 SYSTEM OVERVIEW

The RH CALIBRATOR has a Test Chamber, a menu driven LCD graphics display,
Automatic Balance Cycle (ABC), a selectable analog output, and an RS-232C serial
port.

Figure 3-1 RH Calibrator Panel

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An Air Temperature Probe and a Type D2 Chilled Mirror Sensor are located in the
Test Chamber. The relative humidity and temperature of the chamber are
programmable from the Scrolling Menu.

The 40 x 8 character backlit LCD displays Dew Point (C or F), Chamber
Temperature (C or F), and Percent Relative Humidity simultaneously.

The Automatic Balance Cycle (ABC) can be set to balance the sensor optics at
preset times and intervals or can be initiated manually at any time.

An analog output is available on the Panel as either 0 to 5VDC or 4 to 20 ma, and it
can be set to follow any parameter with individually programmable high and low
points. The output can be set to Track the selected parameter value during the ABC
cycle or Hold the last value prior to the ABC cycle.

The half duplex configured RS-232C serial port can be used to remotely control the
calibrator operation, and to output data to a data recording device.

3.3 OPERATING CONTROLS

The RH CALIBRATOR operates entirely under microprocessor control. State-of-the­art software provides the opportunity to include a flexible, informational, and user
friendly interface. The setup and operation of the control unit can be programmed via
the front panel keypad or the RS-232 serial port.

LCD Graphics Display: Displays three parameters simultaneously, time, date,
operational status, sensor mirror condition, and alerts the user to fault conditions.
When activated from the Scrolling Menu, the AT SETPOINT (chamber
temperature) and the RH SETPOINT (relative humidity), are displayed. The
display of Dew Point may also be selected with the Keyboard.

Keypad: A membrane type keypad allows the user to enter setup and instrument
control information. A Scrolling Menu guides the user through the setup
procedure. The Setup Parameters include RH SETPOINT, AT SETPOINT, time,
date, analog output parameter and scale, ABC start and interval, and serial port
settings.

SERVOLOCK ™: The SERVOLOCK feature continuously displays the servo
control loop status. This is especially useful when the sample dew point is
varying widely or quickly. When SERVOLOCK is displayed, the system is locked
on to and tracking the dew point.

ABC Cycle: The Automatic Balance Cycle checks for proper operation of the
system and re-balances the sensor to compensate for changes in reflectivity of
the mirror due to aging, optics drift, or minor contamination due to impurities in
the sample gas. The on board real time clock permits the user to program the

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ABC cycle to start at any specified time of day and repeat at regular­programmed intervals. The user can therefore program the ABC cycle to occur at
off-hours such as late at night or early morning when the re-balance will cause
the least interruption of the sampling process. The cycle can also be initiated
manually at any time by a pushbutton on the front panel or via the serial port.

The analog output can be programmed to either TRACK or HOLD the information
during an ABC cycle.

Serial Port: The RS-232C serial port can be used to remotely program setup
parameters, initiate an ABC cycle, or output data to a local or remote terminal,
printer, or computer. The data output function outputs, in ASCII format, the date,
time, three parameters, and system status to any RS232C equipped serial
device. The data can be sent on command from the external device or
automatically at programmed intervals. HELP and STATUS menus can also be
displayed to guide the user.

Analog Output: The analog output, either 0-5 VDC or 4-20 ma, is available at
the Panel terminal connector. The output can be set to track any parameter, and
may be independently scaled via the Scrolling Menu.

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4.0 WARRANTY STATEMENT

All equipment manufactured by Edgetech Instruments Inc. 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 Instruments Inc.
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 Instruments Inc. and the directions received for
properly identifying items returned under warranty are followed; and (iv) the
return notice authorizes Edgetech Instruments Inc. to examine and
disassemble returned products to the extent Edgetech Instruments Inc. deems
necessary to ascertain the cause for failure. The warranties expressed herein
are exclusive. There are no other warranties, either expressed or implied,
beyond those set forth herein, and Edgetech Instruments Inc. does not assume
any other obligation or liability in connection with the sale or use of said
products.

Equipment not manufactured by Edgetech Instruments Inc. is supported only to

the extent of the original manufacturer’s warranties

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5.0 EDGETECH INSTRUMENTS INC.’S COMMITMENT
TO QUALITY

Thank you for purchasing one of our products. At Edgetech Instruments Inc.,
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 Instruments Inc.

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6.0 N.I.S.T. TRACEABILITY – WHAT DOES IT MEAN?

The RH-CAL, or Relative Humidity Calibrator, is certified by Edgetech Instruments Inc.
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 the RH-CAL?

The calibration chamber in the RH-CAL can be set by the user to any desired relative
humidity (RH). The instrument measures and controls the chamber RH by measuring
both the air temperature (AT) and the dew point temperature (DP) in the chamber.
Since there is a mathematical relationship between dew point temperature, air
temperature, and relative humidity, a built-in microprocessor can therefore compute the
chamber RH.

Dew Point is a fundamental measurement of humidity. It is not affected by temperature.
In addition, the chilled mirror dew point sensor in your RH-CAL provides a primary
rather then a secondary measurement of dew point temperature.

Both the AT and the DP are measured with 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 in the RH-CAL.

TRACEABILITY:

 1. The precise platinum 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 RH-CAL chilled

mirror dew point sensor, using Edgetech Instruments Inc.’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 their 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 parameter.
AT Air Temperature – the temperature inside the test chamber.
Depression The magnitude of available mirror cooling in the chilled mirror sensor.
Desiccant A chemical material which removes moisture from the air sample and

thereby produces very dry air.
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.
Saturator A device which brings the air sample to 100% RH.
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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8.0 INSTALLATION

8.1 UNPACKING

Remove the RH CALIBRATOR 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 Cleaner Kit included in the shipping
carton.

IMPORTANT:

1. Locate the RH-CAL on a flat horizontal surface. Leave a minimum of 6 inches
(15 cm) on both sides for proper air flow.

2. Before first use, unscrew the Saturator Cap and remove the Shipping Plug
(Red Top/Clear Tube) from the small stainless steel Saturator Air Outlet Tube.
Put the Shipping Plug away in a safe place – you may need it later.

Figure 8-1. Remove Shipping Plug

modifications over this range; only the fuse must be changed if changing from a
nominal 115 VAC to 230 VAC.

Note: The correct fuse is installed at the Factory, depending upon the normally
supplied voltage at the shipping location.

Fuse Location: The AC power line fuse is located behind the left side of the
carrying handle, on a printed circuit board mounted inside the carrying case.

Fuse Values:
For U.S. use (and others): For power line voltage between 100 to 150 VAC, the
fuse type is 3A, 3AG, 250VAC, Slo-Blo. For power line voltage between 150 to
240 VAC, the fuse type is 1.5A, 3AG, 250 VAC, Slo-Blo.
For European use: Use Type T fuses. For nominal 230 VAC, the required fuse
value is 1.6A.

NOTE: Whenever the RH CALIBRATOR
is moved, the saturator Shipping Plug
should be installed to prevent water
leakage.

8.2 WIRING CONNECTIONS

Connect the RH CALIBRATOR to a
grounded, instrument quality power
source of between 100 to 240 VAC, 50-60
Hz. There are no jumper or switch setting

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8.3 WATER FILL

Figure 8-2. Filling the Saturator

Note: Only distilled or deionized
water should be used. The
minerals in tap water may
gradually contaminate the
instrument and cause inaccurate
readings.

With power ON, remove the cap
from the clear water reservoir. Using
the supplied syringe, draw water into
the syringe until full. Place the
flexible hose at the end of the
syringe into the opened Saturator fill tube such that the tip extends below the
clear portion of the fill tube, and depress the plunger. Do not fill above the panel
surface. In case of overfill, draw the excess water into the syringe and bring the
water level below the clear portion of the fill tube. Total capacity of the Saturator
is approximately 40 ml (2 – 3 full syringes). Replace the reservoir cap firmly.

8.4 AIR CONNECTION

(Optional)

A ¼ inch compression fitting is mounted on the panel. In normal portable
operation, it is not necessary to connect anything to this port, since room air is
automatically drawn into the calibrator, through the fitting, by the vacuum pump.
If you prefer to use your own source of instrument quality dry air, a ¼ inch line
may be connected. In this mode, the requirement for periodic maintenance of
the desiccant dryer material is eliminated.

Note: Air line pressure must NOT exceed 5 psig.