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Edgetech RH CAL Operator's Manual

Relative humidity calibrator
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RH CAL
Relative Humidity Calibrator
OPERATORS MANUAL
399 River Road ● Hudson, MA USA 01749
Tel. [508] 263-5900 ● [800] 276-3729 ● Fax [508] 486-9348
E-mail h2o@edgetechinstruments.com ● www.edgetechinstruments .com
Rev. A
March 2011

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Summary of Contents for Edgetech RH CAL

  • Page 1 RH CAL Relative Humidity Calibrator OPERATORS MANUAL 399 River Road ● Hudson, MA USA 01749 Tel. [508] 263-5900 ● [800] 276-3729 ● Fax [508] 486-9348 E-mail h2o@edgetechinstruments.com ● www.edgetechinstruments .com Rev. A March 2011...

  • Page 2: Table Of Contents

    2.0 List of Illustrations 3.0 Introduction 3.1 General Description 3.2 System Overview 3.3 Operating Controls 4.0 Warranty Information 5.0 Edgetech Instruments Inc.’s Commitment to Quality 6.0 N.I.S.T. Traceability – What does It Mean? 7.0 Glossary 8.0 Installation 8.1 Unpacking 8.2 Wiring Connections 8.3 Water Fill...
  • Page 3 12.1 System Status 12.2 Keypad Operation 12.3 Programming the RH-CAL 12.4 Calibrating RH Sensors 12.5 RS-232 Serial Port Setup 13.0 The Chilled Mirror Dew Point Sensor 13.1 Theory of Operation 13.2 Automatic Balance Cycle 13.3 Care and Maintenance of the Sensor 14.0 Maintenance 14.1 Routine Maintenance...

  • Page 4: List Of Illustrations

    2.0 LIST OF ILLUSTRATIONS Page RH Calibrator Panel Removing Shipping Plug Filling the Saturator Basic Block Diagram 10-1 Panel Description 11-1 The Information Display 12-1 Keypad 12-2 Changing the RH Setpoint 12-3 Changing the AT Setpoint 12-4 Selecting Dew or Frost 12-5 Locking In the Changes 13-1 Chilled Mirror Block Diagram 14-1 Cleaning the Mirror...

  • Page 5: Introduction

    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.

  • Page 6: Operating Controls

    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.
  • Page 7 ABC cycle to start at any specified time of day and repeat at regular- programmed 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.

  • Page 8: Warranty Information

    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.

  • Page 9: Edgetech Instruments Inc.'s Commitment To Quality

    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.

  • Page 10: Traceability - What Does It Mean

    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.

  • Page 11: Glossary

    7.0 GLOSSARY Automatic Balance Control – a method of maintaining accuracy in the ABC: presence of contamination and minimizing maintenance requirements. Analog Out A voltage or current that tracks changes in a parameter. Air Temperature – the temperature inside the test chamber. Depression The magnitude of available mirror cooling in the chilled mirror sensor.

  • Page 12: Installation

    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.

  • Page 13: Water Fill

    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.

  • Page 14: Basic Block Diagram Theory Of Operation

    BASIC BLOCK DIAGRAM THEORY OF OPERATION Figure 9-1. Basic Block Diagram...

  • Page 15: Basic Block Diagram Description

    The air flow is than divided and sent to a pair of finely matched volumetric Control Valves. The RH CAL independently modulates the “Dry” and “Wet” valves from full- open to full-closed, or any points between. The “Wet” valve feeds the heated Saturator, which has a water fill mounted on the panel.

  • Page 16: Panel Description

    10.0 PANEL DESCRIPTION 2. AIR DRYER 1. AIR INLET 3. WATER FILL TUBE 4. TEST CHAMBER 5. KEYPAD INFORMATION DISPLAY 7. ANALOG OUTPUT 6. DIGITAL OUTPUT 8. ON/OFF SWITCH Figure 10-1 RH-CAL Panel Description 1. Air Inlet (Sample In) – Brings in room air for use in the system. An Instrument Air line may also be connected.
  • Page 17 4. Test Chamber – Contains controlled RH and Temperature environment for calibrating sensors. 5. Keypad – A pressure-sensitive keypad that allows the user to program setpoints and to control functions. 6. Digital Output – RS-232C serial port for computer communication. 7.

  • Page 18: Information Display Functions

    11.0 INFORMATION DISPLAY FUNCTIONS Figure 11-1. The Information Display 11.1 INFORMATION DISPLAYED The large LCD Display mounted on the Panel provides the user with all the information necessary to properly operate the RH-CAL. It can be used as the primary interface with the instrument, showing status of all parameters, and allowing calibration points to be easily programmed.
  • Page 19 Note: The above three parameters may be programmed to be displayed in any desired sequence. S_HEAT DISPLAY: Cycles on and off to show when power is applied to Saturator heater. BAR GRAPH DISPLAY: The Bar Graph displays a picture of the dew layer on the chilled mirror surface.

  • Page 20: Operating The Rh Calibrator

    Turn the Power Switch to the ON position. The small adjacent indicator lamp will light, and the Digital Display will: (1) light up; (2) briefly indicate RH CALIBRATOR by EDGETECH INSTRUMENTS INC.; and (3) go into the normal display mode. A hum will be heard, indicating that the fans and vacuum pump are operating.

  • Page 21: Keypad

    from Fahrenheit to Centigrade when the C/F key is pressed. The analog output level does not change when C/F is toggled, because ranges are converted. MABC Starts the Manual ABC cycle. If the RH CALIBRATOR is already in an ABC cycle, this key cancels the ABC cycle.

  • Page 22: Programming The Rh-Cal

    12.3 PROGRAMMING THE RH-CAL RH SETPOINT: The relative humidity of the sample chamber can be set from 5 to 95% and will operate automatically at the factory default setting unless reprogrammed. The RH SETPOINT will appear in the lower portion of the main display. To change the setting, press ENT to enter the SCROLL MENU, move down to the RH SET box, press ENTER and use the keypad to make the change.
  • Page 23 sample chamber can be set from 10 - 50 Deg. C. (40 -122 Deg. F.) and will operate automatically at the factory default setting unless reprogrammed. If enabled, the AT SETPOINT will appear in the lower right portion of the main display. SYSTEM: Time and date on the main display can be changed here.

  • Page 24: Selecting Dew Or Frost

    ABC Status: ON ABC Start Time: 00:00 Hrs. ABC Interval: 06:00 Hrs. Analog Hold: OFF Analog Output: RH Parameter, 0 – 100% Serial Output: OFF Serial Output Interval: 1 minute Baud Rate: 9600 CALCULATING RH USING EITHER DEW OR FROST Figure 12-4.

  • Page 25: Calibrating Rh Sensors

    LOCKING IN THE PROGRAM CHANGES Once the modifications to the previously programmed settings have been inserted to your satisfaction, you must lock them in. To do this, press ESC on the Keypad. The KEEP CHANGES? screen will appear. Figure 12-5. Locking In the Changes If you are not sure, or if you would like to make additional modifications to the program, press ESC on the Keypad and start over.

  • Page 26: Rs-232 Serial Port Setup

    4. If your sensor will be used to monitor a process (for example) that will always go from low RH to high RH, then calibrate it that way. The hysteresis error will be eliminated. 5. Allow sufficient time for chamber stabilization before calibrating sensors. In addition, allow sufficient time for the Sensor Under Test to completely equilibrate before calibrating each point.
  • Page 27 RS-232 COMMANDS AND PARAMETER SETTING General Several of the setup and operating features of the RH CALIBRATOR are available via the serial port. Commands can be upper or lower case. When any key is pressed, the RH CALIBRATOR will respond with “Input: “ and the key that was pressed “key”.
  • Page 28 ABC Analog Hold Typing the letters ‘AH’ will toggle the ABC Hold feature on or off. If ABC Hold is on, the analog and serial outputs will be held at the values just prior to initiating the ABC Cycle. The serial output will contain the message “ABC Hold”. The hold will be released when the ABC Cycle is complete and the instrument has stabilized back on the dew point.
  • Page 29 NOTE: After an extended period of time in the cool mode, excess moisture or frost will form on the mirror. It may be necessary to “Manually Heat” the mirror to shorten the drying time. Time Type the letter “T” and press ENTER. The time format is: Hours:Minutes:Seconds.

  • Page 30: The Chilled Mirror Dew Point Sensor

    13.0 THE CHILLED MIRROR DEW POINT SENSOR Figure 13-1. Chilled Mirror Block Diagram 13.1 THEORY OF OPERATION Dew Point is defined as the temperature that moisture just begins to condense on a surface. The chilled mirror dew point sensor measures this parameter directly. A highly reflective rhodium mirror is mounted to a solid state heat pump, or thermoelectric cooler.

  • Page 31: Automatic Balance Cycle

    Edgetech Instruments Inc. RH Calibrator. 13.2 MIRROR AUTOMATIC BALANCE CYCLE (ABC) The Automatic Balance Cycle is an important electronic feature of the RH CAL that allows much longer operation of the system without any maintenance. At least 90 days is typical. As contamination from the air sample gradually builds up on the mirror surface, an error in the indicated dew point reading could eventually occur.

  • Page 32: Care And Maintenance Of The Sensor

    13.3 CARE AND MAINTENANCE OF THE CHILLED MIRROR SENSOR Although the ACB cycle greatly minimizes the requirement for mirror cleaning, eventually the system will have to be shut down and the mirror cleaned. A CLEAN MIRROR indication displayed at the end of the ABC cycle tells the user when cleaning is required.

  • Page 33: Maintenance

    14.0 MAINTENANCE 14.1 ROUTINE MAINTENANCE To maintain the maximum in accurate and reliable operation of any optical chilled mirror system, a periodic maintenance program should be established. 14.1.1 MIRROR CLEANING SCHEDULE The buildup of contamination on the mirror surface normally occurs very slowly. Over time, particulates and other matter present in the sample gas that are not captured by filters build up on the mirror.

  • Page 34: Dryer Tube Maintenance

    distilled water, and wipe the mirror and surrounding areas again. 4. Dry these areas thoroughly with a clean, dry cotton swab. 5. Replace the sensor cover and the sample chamber cover. 6. Press the “HEAT” key to return to normal operation. 7.

  • Page 35: Filling The Saturator

    The desiccant pellets may be reclaimed by heating, which will cause the color to return to blue. You may also refill the cylinder with fresh pellets. Reconnect the tubing and reinstall the cylinder. To reclaim the pellets: 1. Unscrew the end cover, and remove the pellets from the tube. Spread the material in thin layers on a flat oven-proof tray.

  • Page 36: Replacing The Fuse

    14.2 REPLACING THE FUSE The AC power line fuse is located inside the top portion of the AC Power socket on the left side of the carrying case of the RH-CAL. A spare fuse is also supplied in the fuse holder.

  • Page 37: Dip Switch Configuration

    Figure 14-5. DIP Switch Configuration: SWITCH NUMBER OUTPUT Where: O = Open 4 - 2O mA C = Closed 0 - 20 mA 0 - 24 mA 0 – 5 VDC...

  • Page 38: Specifications

    15.0 SPECIFICATIONS RH and AT Operating Ranges RH Range: 5 % to 95 % for AT = 15 to 50 C 15 % to 95 % for AT = < 15 C AT Range: 10 °C to 50 °C RH Accuracy Range: 5 % to 50 % +/- 0.5 RH % 51 % to 75 %...
  • Page 39 Display LCD graphics backlit display 0.25-in. high digits Analog Output Selectable for Voltage or Current Voltage 0 to +5 VDC, scaleable from -50 to +100ºC (-58 to +212ºF) ±0.2 % accuracy. 1 K ohms minimum load resistance. Current 4 to 20 mA, scaleable from -50 to +100ºC (-58 to +212ºF). 1000 ohms maximum loop resistance.
  • Page 40 Mounting Configuration Carrying Case Material: Ultra High-impact Structural Copolymer Dimensions 52.4W x 43.7D x 21.7H cm 20-5/8W x 17-3/16D x 8-9/16H in. Power Requirements 100 to 240 VAC, 50-60 Hz, 150 Watts maximum Fuse For U.S. Operation: 100 - 150 VAC Operation: 3A, 3 AG, 250 VAC, Slo-Blo 150 - 240 VAC Operation: 1.5A, 3 AG, 250 VAC, Slo-Blo...
  • Page 41 Notes...

This manual is also suitable for:

Rh-cal

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