General Eastern Humilab Operating Manual
Humi
Lab
Relativ
e Humidity Generator
Oper
ator’s Manual
500 Research Drive
Wilmington MA 01887-4498
Tel: 800-33HUMID (800-334-8643)
Fax: 978-203-1919 www.generaleastern.com
Safety:
T
his manual as well as safety labels posted on the instrument use the following safety
alerts to draw your attention to special safety instructions that should be followed.
C
CAU
TION:
W
ARNING:
AUTI
Hazards or unsafe practices could result in electrical shock, minor
injury, or product damage.
W
AR
Refer to accompanying document for additional information.
ON
NING
ALERT
A
LERT:
W
indows and Windows XP are trademarks of Microsoft Corp.
The information in this manual is believed to be reliable. However, GE General Eastern makes no warranty, expressed or implied, as to its
accuracy and assumes no liability arising out of its use by others. We reserve the right to change this manual without prior notice.
Document No. A40241708
Revision B.00 ECO #6498
June 2004 Printed in U.S.A
Copyright © 2003, 2004 GE General Eastern
Earth ground connection; removal could result in electrical shock,
minor injury, or product malfunction.
GE General Eastern
500 Research Drive
Wilmington, MA 01887
Tel: 978 203 1900
Fax: 978 203 1919
Email: generaleastern@ge.com
Web: www.generaleastern.com
C
ONTENTS
INTRODUC
CHAPTER 1 — INST
CHAPTER 2 — OPERATION
TION
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
About GE General Eastern - - - - - - - - - - - - - - - - - - - - - - 1
Overview of the Humilab - - - - - - - - - - - - - - - - - - - - - - - 2
About this Owner’s Manual - - - - - - - - - - - - - - - - - - - - - - 2
ALLATION AND INITIAL SETUP
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4
Pre-Installation - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4
Components shipped with the Humilab - - - - - - - - - - - - - - - 4
System diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
Installation - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6
Place the Humilab at its operating site - - - - - - - - - - - - - - 6
Connect a dry gas source (optional) - - - - - - - - - - - - - - - - 6
Electrical connections - - - - - - - - - - - - - - - - - - - - - - - - 8
Rear input/output fitting connections - - - - - - - - - - - - - - - - 9
Initial setup and water fill - - - - - - - - - - - - - - - - - - - - - 11
Chilled mirror setup - - - - - - - - - - - - - - - - - - - - - - - - 12
Initialize the dew point sensor - - - - - - - - - - - - - - - - - 12
Clean and balance the dew point sensor - - - - - - - - - - - - 13
Shipping the Humilab - - - - - - - - - - - - - - - - - - - - - - - 15
- - - - - - - - - - - - - - - - - - - - - - - - 16
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - 16
Front panel displays and switches - - - - - - - - - - - - - - - - - 17
Performing routine calibrations - - - - - - - - - - - - - - - - - - - 20
Chamber response time - - - - - - - - - - - - - - - - - - - - - - 21
- - - - - - - - - - - - 4
CHAPTER 3 — USING THE P
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - 22
Installing the Prostep software - - - - - - - - - - - - - - - - - - - 23
Running Prostep - - - - - - - - - - - - - - - - - - - - - - - - - - 24
CHAPTER 4 — T
Overview - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 30
Divided flow - - - - - - - - - - - - - - - - - - - - - - - - - - - - 30
The Humilab chilled mirror controller - - - - - - - - - - - - - - - 31
HEORY OF OPERATION
What is optical condensation hygrometry? - - - - - - - - - - - 32
General description of the chilled mirror hygrometer system - - 33
Chilled mirror hygrometer system theory of operation - - - - - 33
ROSTEP SOFTWARE
- - - - - - - - - - - - - - - - - 30
- - - - - - - - - - - - 22
CHAPTER 5 — MAINTENANCE AND T
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - 35
Basic maintenance - - - - - - - - - - - - - - - - - - - - - - - - 35
Reference measurement maintenance - - - - - - - - - - - - - - 36
Mirror maintenance - - - - - - - - - - - - - - - - - - - - - - - - - 36
Cleaning the sensor mirror - - - - - - - - - - - - - - - - - - - 36
Balancing the sensor optics - - - - - - - - - - - - - - - - - - - 37
Field replacement of the sensor mirror - - - - - - - - - - - - - - 40
Annual recertification - - - - - - - - - - - - - - - - - - - - - - - - 41
Troubleshooting the Humilab, system diagnostics - - - - - - - - - - 41
Is the system operating correctly? - - - - - - - - - - - - - - - - 41
ROUBLESHOOTING
- - - - - - - - 35
APPENDIX A — SPEC
APPENDIX B — HUMILAB CHILLED MIRROR H
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - 45
System components - - - - - - - - - - - - - - - - - - - - - - - - - 45
Front panel operation and displays - - - - - - - - - - - - - - - - - 46
Displays - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 47
Switches - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 48
Option selections using the display switch - - - - - - - - - - - - 49
A simplified explanation of the option selection system - - - - - 49
A more rigorous explanation of the option selection system - - - 50
RS-232c re-programming mode - - - - - - - - - - - - - - - - - - - 52
The Main Menu - - - - - - - - - - - - - - - - - - - - - - - - - 53
Scale outputs - - - - - - - - - - - - - - - - - - - - - - - - - - 53
Set balance type - - - - - - - - - - - - - - - - - - - - - - - - - 54
Set RS-232 units - - - - - - - - - - - - - - - - - - - - - - - - - 55
Display option - - - - - - - - - - - - - - - - - - - - - - - - - - 56
Set averaging - - - - - - - - - - - - - - - - - - - - - - - - - - 57
Service and troubleshooting procedures - - - - - - - - - - - - - - - 58
Helpful hints - - - - - - - - - - - - - - - - - - - - - - - - - - - - 61
Time response - - - - - - - - - - - - - - - - - - - - - - - - - - 61
Mirror cleanliness - - - - - - - - - - - - - - - - - - - - - - - - 61
APPENDIX C — CONFIGURING THE R
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - 65
Establishing RS-232 communications - - - - - - - - - - - - - - - - 65
Using RS-232C communications - - - - - - - - - - - - - - - - - - 66
RS-232C operate mode - - - - - - - - - - - - - - - - - - - - - 66
Computer connections - - - - - - - - - - - - - - - - - - - - - 67
IFICATIONS
- - - - - - - - - - - - - - - - - - - - - 43
YGROMETER DETAILS
S-232 INTERFACE
- - - - - - - - - 65
- - 45
APPENDIX D — HUMIDITY EQUATIONS AND CONVERSION CHAR
APPENDIX E — W
ARRANTY INFORMATION AND RETURN PROCEDURES
TS
- 68
73
Ab
out GE General Eastern
GE General Eastern is devoted to the design and manufacture of
accurate, reliable and rugged humidity measuring equipment. We
specialize in providing solutions for applications where humidity
measurements are critical.
There are many ways to make humidity measurements, and no
single humidity sensor meets all requirements for all applications.
Our variety of sensor types — including chilled mirror, lithium
chloride, capacitive oxide, capacitive-resistive, resistance polymer,
and wet bulb — can precisely determine dew point, parts per million
by volume, mixing ratio, absolute humidity, relative humidity, and
other parameters.
In keeping with GE General Eastern’s philosophy of providing the
best solutions to humidity measurement problems, we offer the
following products and services:
• high quality state-of-the-art instrumentation to assure
excellent performance
• a broad range of humidity instruments capable of covering
virtually any humidity measurement application
• full applications assistance to help you choose the sensor that
is best for your needs
• worldwide superior service, should it ever be needed
If you have questions about a particular measurement problem, we
invite you to call and discuss your application with one of our
engineers. Call 800-33HUMID (800-334-8643). If you’re calling
from Massachusetts or outside the United States, call
978-203-1900. Our fax number is 978-203-1919.
GE General Eastern’s website (www.generaleastern.com) has information about our other products as well as technical papers and
applications notes on humidity measurements.
Intr
oduction
Intr
oduction
Page
1
Ov
erview of the Humilab
T
he Humilab Relative Humidity Generator is designed to perform
U.S. National Institute of Standards and Technology (N.I.S.T.) traceable calibration of RH instruments and/or several smaller transmitters.
The Humilab design is based on the proven divided flow technology. Divided flow in the time domain excels as a reliable
method for accurately controlling relative humidity at a fixed
temperature. Temperature stability is ensured by a water jacket
surrounding the calibration chamber.
Continuous digital control, using a built-in GE General Eastern
N.I.S.T. traceable chilled mirror dew point hygrometer, makes the
Humilab a traceable relative humidity transfer standard with which
to calibrate other devices. Calibrations meeting the requirements of
ANSI Z540-l-1994, MIL-STD 45662A, 10CFR-50, and ISO 9001 may
be performed.
The included Prostep software allows you to use your PC to upload
a control profile via the RS-232 port, enabling an entire calibration
cycle to be run.
Ab
out this Owner’s Manual
T
his manual provides the information you will need to set up, use,
and maintain the Humilab Relative Humidity Generator. Please
read and follow these instructions carefully to ensure that the
instrument provides the precise and reliable humidity measurement and control that you have come to expect from GE General
Eastern.
Page
F
Icons
2
our categories of information are presented with an accompa-
nying icon for quick identification.
The exclamation mark within a triangle indicates that the accompanying information is important to the correct operation of the
equipment. You should take particular care to observe this information because it ensures optimum operation and avoids potential
damage to the unit.
Intr
oduction
T
he lightning bolt within a triangle indicates that the accompanying information is important to the safety of the operator. Failure
to heed this information will place the operator in danger. This
symbol must not be ignored.
The ground symbol indicates points that must be connected to
earth ground. Failure to connect, or removal, could result in electrical shock, minor injury, or product malfunction.
The pointing hand icon is used to indicate information that is
related or simply additional to the surrounding text. This information is not required for proper operation, nor will any harm arise
from not applying this information.
Intr
oduction
Page
3
Chapter 1 — Inst
Intr
oduction
T
his chapter explains site requirements for the Humilab system,
what is shipped with the unit, how to install the Humilab, and how
to set it up and perform the necessary procedures to ensure efficient and reliable operation to meet your calibration requirements.
Pr
e-Installation
Bef
ore you proceed to install your Humilab, ensure that you have
chosen a site suitable for the effective and efficient operation of the
instrument.
A location should be found for the Humilab where the ambient
temperature is reasonably constant. This is usually the case in a
calibration laboratory. Ideally, the room should be stable within
±1°C, between 20°C and 30°C. Ensure that the table or lab bench is
level.
The water jacket surrounding the test chamber and the 1/2” thick
Lexan cover above it effectively isolate the chamber from
short-term temperature fluctuations. However, longer term
changes in room ambient temperature may cause a temporary
chamber error until the system equilibrates to the new ambient
temperature. Therefore, temperature stability of the room is important.
allation and Initial Setup
Components
Page
4
CA
UTION:
T
wo people are required for moving this system.
shipped with the Humilab
T
he following items are packaged with the Humilab:
• cover (removed for shipment)
• Certificate of Conformance
Chapter 1 — Installation and Initial Setup
Optional
equipment
•
maintenance kit
(Additional kits are available through G
•
mixing/workspace plate
• desiccant cartridges (2)
• rubber stopper
• AC power cord
• RS-232 cable
• mating analog output connector
• transportation case
• CD-ROM containing this manual, HCON Humidity Conversion software, and Prostep software
•
temperature bath/circulator (for maintaining a stable chamber temperature from 20°C to 30°C)
If an item is missing, contact GE General Eastern. Our phone
number and address are found on page 1.
EI’s Service Department)
System diagr
Chapter 1 — Installation and Initial Setup
am
Interconnection of the HumiL
Figure 1.
ab’s components is shown in
Page
5
Analog
outputs
Cooling fan
Reference port
Controller port
Humilab
(rear view)
Dry air input (optional)
Neslab
Chiller
(optional)
Inst
allation
Place the
Humilab at its
operating site
Carefull
room behind the unit to make the necessary gas, drain, and
optional chiller connections on the back panel. The two data cables
(an RS-232 cable and an analog output cable) can also be installed
at this point.
Connect
a dry
gas source
(optional)
A dry gas source can be utilized to impro
desiccant material and provide the user with less frequent desiccant replacement.
The HumiLab does not require an external dry gas source to
operate. The unit is equipped with a desiccant cartridge that
provides the Humilab with a –40°C dew point dry gas. The unit is
designed to operate for approximately 24 hours of continuous
usage (at an ambient humidity less than 50%) before having to
replace the desiccant.
AC power
y move the Humilab to its intended site. Leave enough
Drain
Figure 1 — System interconnection diagram
PC
ve the longevity of the
Page
Gas r
equirements.
be –40°C or lower for operation over the full specified range.
6
If a dry gas source is used, the frost point should
Use
Chapter 1 — Installation and Initial Setup
clean, oil-free gas, regulated at 1 to 2 psig at 5 lpm (minimum).
Connect the dry air or dry nitrogen source using the 1/4”
“instant-on” DRY AIR IN connector on the rear of the unit. See
Figure 2, Humilab Rear View.
Figure 2 — Humilab rear view (gas, A/C, and signal connections)
Chapter 1 — Installation and Initial Setup Page 7
Electrical connections
s
Electrical connections to the Humilab are made on the rear panel
as shown in Figure 3.
A
B
ANALOG OUTPUTS
REFERENCE RS-232 CONTROLLER RS-232
LINE
Figure 3 — Humilab electrical connection
C
D
A. Analog outputs. Analog outputs are available to the operator via
the DB-15 connector located on the rear I/O panel. A cable suitable
for connecting to a terminal block is included. The connector
pinout is listed below.
DB-15 Pin No. Function
1 RH 4–20 mA (+)
2 RH 0–5 V (+)
3 Temp 4–20 mA (+)
4 N/C
5 Temp 0–5V (+)
6 Status
7 N/C
8 N/C
9 Service
10 Gnd (Rtn)
11 N/C
12 N/C
13 N/C
14 N/C
15 N/C
Page 8 Chapter 1 — Installation and Initial Setup
B. RS-232 Reference Port. This connector is used for diagnostics
s
when the LOOP switch is in the OPEN LOOP position. In CLOSED
LOOP mode, it transmits the digital outputs of the hygrometer: dew
point, temperature, and RH.
C. RS-232 Controller Port. This connector is used when down-
loading humidity profiles from Prostep into the HumiLab.(see
Chapter 3).
D. AC receptacle. The AC input power is connected to the power
receptacle. The input voltage is noted on the label to the right. The
input voltage is configured at the factory and must be determined
prior to shipment.
Power Requirements 103–127 VAC
48–66 Hz, 80 VA max
Fuse Type 1A Type T .5A Type T
E. Cooling fan (not visible). The fan is used for cooling the elec-
tronics. The fan must stay clean and clear of any obstruction to
prevent damage to the internal electronics.
Rear input/output fitting connections
Mechanical connections to the Humilab are made on the rear panel
as shown in Figure 4.
B
COOLANT IN DRY AIR IN
COOLANT OUT DRAIN
C
Figure 4 — Humilab mechanical connection
198–264 VAC
48–66 Hz, 80 VA max
A
D
Chapter 1 — Installation and Initial Setup Page 9
A. Dry air in. A dry air supply can be connected to this port. The
dew point of the dry air must be at or below –40°C for proper
full-range operation. The flow rate requirement is 1 to 2 psig at 5
liters per minute (minimum). If a dry air supply is not available,
then this port must be left open to the atmosphere. The internal
pump will draw the ambient air through the desiccant cartridge to
supply the HumiLab with the proper supply of dry air.
B. Coolant In. For optimum performance, an optional temperature
bath/circulator should be connected to provide a stable water and
chamber temperature. Connect the chiller’s output port to this
Coolant In port.
C. Coolant Out. Connect the temperature bath/circulator’s input port
to the coolant-out port of the HumiLab.
D. Drain. This port allows the operator to easily drain the saturator
before transporting or storing the unit. Simply place a 1/4” tube
into a bucket and press the other end into the drain fitting until it
stops. Water will immediately begin to drain into the bucket. To
remove the tube from the fitting, depress the black outer ring and
pull out the tubing. A built-in check valve prevents water from
running out of the drain port when the tubing is not in place.
Coolant
connections
Page 10 Chapter 1 — Installation and Initial Setup
The HumiLab is equipped with 1/4” “instant on” coolant fittings
that require no tools for installation. These fittings will accept many
types of hard-wall tubing such as Teflon, stainless steel, or
Impolene. To insert the tubing, simply press the tubing into the
connector as far as it will go. Pull gently on the tubing to ensure
the connections are secure.
To remove the tubing from the “Instant On” fittings, simply depress
the black outer ring and pull the tubing out. The coolant fittings
are equipped with built-in check valves that enable the operator to
easily remove the coolant lines with minimal fluid loss.
If the optional chiller is used to accurately control the chamber
temperature, connect the chiller output to the “Coolant In” fitting
on the HumiLab and connect the chiller inlet to the “Coolant Out”
fitting.
Initial setup and water fill
Distilled water is recommended for trouble-free operation. Always
add water with the power turned off (the water level may pulse up
and down during normal operation). After the water chamber has
been filled (or refilled), allow sufficient time (typically one hour) to
equilibrate the water temperature.
1. Set up the unit on a flat surface.
2. Pour in one gallon of clean distilled water.
3. Install the drain line in the rear drain port, and drain out
enough water (about one cup) to ensure that the drain line is
full of water. This procedure is needed for proper water level
indication.
4. Remove the drain line and pour in an additional 1¼ gallons of
distilled water. Wipe up any spillage.
5. Install the dry line, connecting to a source of dry air, if available (–40°C DP dry air or nitrogen, 15–16 psig, 4–5 l/m flow).
If running from a desiccant cartridge, make sure the cartridge
is fully seated and the desiccant color is a minimum of 75%
blue throughout the length of the tube. Replace the cartridge
or desiccant if necessary.
6. Install the unit’s cover.
7. Install the power cord and turn the unit on. Set the controller
to 80–90% RH.
8. Check the water fill level indicator and make sure the level
has not increased above the fill line and that the overflow line
does not leak water (front left-hand corner of unit). If the
water fill level rises sharply or the overflow tube leaks, check
the wet gas tube inlet ports for obstructions.
9. Run the unit for 15–30 minutes and inspect for the absence of
water in the bottom of the wet line ports located at the bottom of the tank I/O block (near 1111H sensor). If water is
present, soak it up with a cotton swab or absorbent cloth, napkin or towel.
10. Perform mirror cleaning and balance procedure as described
in “Mirror maintenance” on page 36.
Chapter 1 — Installation and Initial Setup Page 11
Chilled mirror setup
The GE General Eastern HumiLab is shipped with the chilled
mirror sensor (1111H-SR) and temperature probe (T-100) already
installed.
Initialize the
dew point
sensor
Although it was initialized at the factory, the dew point sensor
bridge should be initialized again to compensate for any change
during shipment. This is accomplished by cleaning and balancing
the sensor as described below. Figure 7, shows the location of the
switches and LEDs on the front panel. Chapter 2 contains a
complete description of the operating procedures.
Figure 5 — Front Panel Controls
1. Plug the A/C power cord into a wall socket.
Page 12 Chapter 1 — Installation and Initial Setup
2. Turn ON the power switch located on the back right side of
the Humilab near the bottom.
The digital LED displays will light, and the generator will go
through a self check cycle. The letter “P” (for Pacer®) will be lit
on the front panel (C in Figure 5). (See Appendix B, page 45
for information on the Pacer feature.)
3. Wait for the Pacer cycle to complete (approximately three
minutes).
4. On the front panel, set the LOOP switch (K) to the CLOSED
LOOP position. (Depress the top of the rocker switch, toward
the filled circle.)
Clean and
balance the
dew point
sensor
The next steps are required to clean and rebalance the dew point
sensor. This normalizes the system, and prepares it for proper operation.
1. Press the SENSOR switch (F) to the HEAT position.
2. Open the test chamber cover and remove the white dust
cover.
3. Locate the sensor cleaning solution (in the GE General Eastern Maintenance Kit). Wet a cotton swab with the blue cleaning solution, and rub it lightly over the mirror. Lightly buff
the mirror dry with a clean, dry swab. Note: If you don’t have
the supplied cleaning solution, a solution of two parts rubbing alcohol to one part distilled water may be substituted.
4. Replace the sensor cover. Be sure that the cover is installed so
that the sensor balance screw aligns with the hole in the
cover.
Do not attempt to operate the sensor without the cover. It is
an optical device and will be offset by overhead light.
5. A vertical LED light bar indicates balance status. Either 3, 2, 1,
or zero horizontal bars will be lit. Locate the Balance, or Bias,
adjustment screw at the top of the sensor. See Figure 6. Using
the small screwdriver supplied in the maintenance kit, slowly
rotate the screw until only the bottom bar is illuminated. (The
Chapter 1 — Installation and Initial Setup Page 13
number of bars is increased when you turn the screw counterclockwise.) The optical bridge has now been balanced.
Figure 6 — 1111H Sensor Balance Adjustment Screw Location
6. Place the HEAT switch back in the OPERATE position.
7. Run the instrument through another Pacer cycle. (Momentarily press the INITiate switch.)
The letter “P” will light, and the displays will be frozen for several minutes as the cycle proceeds. At the end of that time,
the “P” will go out, and the left-hand displays will read the
actual percent R.H. and temperature in the test chamber.
8. Use the SETPOINT switch to select 30% RH by pressing on the
upper or lower side of the switch as required.
The display will scroll, one decade at a time, to the desired
reading. Release the switch when that point is reached.
9. Run the chamber for at least one hour, until the water surrounding the chamber assumes ambient laboratory temperature and the temperature equilibrates to ±0.2°C or better.
10. Use the SETPOINT switch to select 00.0 %RH and allow 30 to
45 minutes for the chamber to dry down.
Page 14 Chapter 1 — Installation and Initial Setup
Shipping the Humilab
This procedure describes the process the customer should follow
before shipping the HumiLab to an off site location or shipping the
unit back to GE General Eastern.
1. Remove A/C power from the unit and disconnect the dry gas
supply.
2. Connect a 1/4" O.D. drain line to the drain port located in the
rear of the unit. For customer convenience, an impolene drain
line is provided. Otherwise any 1/4" hard wall tubing will do.
3. Visually interrogate the unit through the fill port to determine if all the water has been removed. If water is still visible,
then the unit may have to be tilted towards the back and to
the left with the drain tube still attached.
4. The temperature bath/circulator lines need to be drained
prior to shipment. Insert the drain tube provided into the
COOLANT OUT port connector. Insert a short 1/4" tube into the
COOLANT IN port connector. This will allow the coolant to be
removed from the temperature coil. This will prevent the temperature coil from freezing during transport and possibly
causing damage to the unit. A slightly pressurized air line
could be used to help facilitate the draining process.
5. Place the mix tray inside of the chamber and fill the chamber
with bubble-pak to prevent any sensor damage and keep the
tray from moving during shipment. Place the cover on top.
Place the rubber stopper (supplied) into the fill port located at
the top front left corner.
6. Place the HumiLab into the transportation case (supplied).
The unit is now ready to be transported.
Chapter 1 — Installation and Initial Setup Page 15
Introduction
Chapter 2 — Operation
The Humilab is very simple to operate. Minimal operator training is
required for successful calibration of humidity recorders, transmitters, or hand-held portables. Typically, only the R.H. setpoint
selector switch is used in a calibration. All other switches are set as
desired and then left in position.
Front panel switch settings are described in this chapter. More
detail is available in Appendix B. For quick reference, the following
settings are typical for most applications:
• Power Switch: ON (mounted on rear of unit)
• Sensor Switch: OPERate
• Display Switch: OPERate
• Loop Switch: Closed Loop (Set to the filled-in circle) for operation; Open Loop (open circle) for uploading profiles
• Balance Switch: Center position
• Auto/Cal Switch: OPERate
• Setpoint: Set to desired chamber humidity
Page 16 Chapter 2 — Operation
Front panel displays and switches
Refer to Figure 7 as you review the following descriptions of the
front panel displays and selector switches.
Figure 7 — Front Panel Controls
The Humilab, as shipped, is set up by the factory for normal operation. The two upper digital displays read Percent RH and Temperature in °C. The lower digital display shows the desired chamber set
point.With the exception of the setpoint selector switch, the other
front panel switches are seldom used in day-to-day operation.
However, they are included in case you wish to make changes to
normal default operation and for system testing.
Appendix B contains information on changing factory-set defaults.
A. HUMIDITY Display. This display is shipped from the factory set
for percent relative humidity. Please refer to Appendix B for more
information.
Chapter 2 — Operation Page 17
If you wish to perform dew point calibrations in the test chamber,
the display may be reprogrammed to read dew point.
B. CONTROL STATUS Indicator. The green control indicator advises
you that the control loop that maintains the dew layer on the
chilled mirror is operating correctly, and that there is a proper layer.
When lit, you may consider it to be an indication that the chilled
mirror humidity measurement is valid. Conversely, if the green
indicator is not lit, you should wait until it lights before performing
calibrations.
C. STATUS Window (humidity). A green letter “S” (for Service) in this
window advises the operator that the sensor mirror has become
contaminated, and requires cleaning.
If you are readjusting the sensor optical balance, a light bar appears
in this window. See “Balancing the sensor optics” on page 37 for
details.
This window will show various indications while reprogramming
the display units or analog outputs. See Appendix B.
D. DISPLAY Switch. The DISPLAY Switch is normally used in the
center OPERate position.
This rocker switch is used to reprogram measurement units and to
check the scale factor of analog outputs.
In the standard configuration, the analog output scale factors can
only be changed using the RS-232 port, to ensure that they are not
changed accidentally. If you wish to reconfigure the system so that
these parameters can be changed via the front panel, see Appendix
B.
E. BALANCE Switch. This switch is normally operated in the lower
AUTOmatic position.
In the AUTO position, the instrument will go through a normal
Pacer® cycle every 12 hours, rebalancing the dew point sensor
bridge and determining whether it requires cleaning.
In the MANual center position, there will be no automatic Pacer
cycles, only those initiated manually (if desired).
Page 18 Chapter 2 — Operation
In the manual position, you will never see the “S”ervice light displayed, telling you that the sensor mirror needs cleaning.
The upper (INITiate) momentary position manually triggers a Pacer
cycle.
F. SENSOR Switch. The SENSOR switch is typically kept in the center
OPERate position.
This switch allows you to over-ride the automatic mirror control
loop, and force the mirror temperature up or down, causing it to
heat or cool. These are test positions used for sensor diagnostics.
G. TEMPERATURE Display. As shipped from the factory, this display
reads temperature in °C. It may be factory or field programmed to
read °F if desired. See Appendix B.
H. STATUS WINDOW (Temperature). This window provides the oper-
ator with programming status for the Temperature display when
programming Units or Outputs. See Appendix B.
I. SETPOINT Display. This display window shows the relative
humidity setpoint that has been programmed in the chamber.
J. SET (SETPOINT) Switch. This switch allows you to select a
humidity setpoint in the display window. Scroll to the desired value
by incrementing or decrementing, one decade at a time, until the
desired value is reached.
K. LOOP SELECT Switch. This selector is normally kept in the Closed
Loop position (up, toward the filled-in circle).
In the Closed Loop position the chilled mirror hygrometer controls
the chamber relative humidity. In the Open Loop position, you can
download humidity profiles from the Prostep software program,
and you can perform diagnostics if necessary (see Chapter 3).
L. CAL/AUTO Switch. This switch is typically kept in the center posi-
tion.
When this switch is pressed into the momentary CALibrate setting,
the system begins the automatic 9-hour recalibration cycle.
Chapter 2 — Operation Page 19
If you ever accidentally switch the Humilab to the “CAL” mode,
simply shut the power OFF and then ON using the power switch
(on the rear panel) to reset to normal operation.
Performing routine calibrations
The unit has been calibrated at the factory. Field calibration is only
required if the measured humidity deviates from the setpoint
humidity by more than 1% RH after one hour.
With the selector switches preset to the proper positions for normal
operation, calibration may be performed as follows:
1. Insert the item(s) to be calibrated into the Humilab humidity
chamber. Run power cables via the top cover to the transmitter.
2. Select the proper RH Setpoint.
When this switch is held up (for higher humidity) or down (for
lower humidity), the digital set point display will scroll toward
the desired set point. First the least significant decade will
change, and then successively more significant decades will
change. Release the switch when the desired humidity is reached.
It may be easier to stop a few counts before the desired reading,
and allow the least significant unit display to move in 0.1%
R.H. steps to the set point.
3. Allow 40 to 60 minutes equilibration time.
The R.H. in the Humilab cavity will gradually move toward the
set point. For the first 20–30 minutes, there will be no
closed-loop feedback. After the loop is controlled, a correction
will be made every 5 minutes.
4. Calibrate as required.
Relative humidity is a function of temperature as well as moisture
content. If you are calibrating a device (such as a humidity transmitter) that generates heat, locate it near the center of the cavity.
This will allow the HumiLab’s temperature sensor to quickly
sense the temperature change and correct for it.
Page 20 Chapter 2 — Operation
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