LI-COR LI-610 Service manual

LI-610
Portable Dew Point Generator
Instruction
Manual
®

LI-610
Portable Dew Point Generator
Operating and
Service Manual

ii
NOTICE
The information contained in this document is subject to change without notice.
LI-COR MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS MATERIAL, INCLUDING, BUT
NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. LI-COR shall not be liable for errors contained herein or for incidental or consequential
damages in connection with the furnishing, performance, or use of this material.
This document contains proprietary information which is protected by copyright. All rights are reserved. No part of
this document may be photocopied, reproduced, or translated to another language without prior written consent of
LI-COR, Inc.
© Copyright 1991, LI-COR, Inc.
Printing History
New editions of this manual will incorporate all material since the previous editions. Update packages may be used
between editions which contain replacement and additional pages to be merged into the manual by the user.
The manual printing date indicates its current edition. The printing date changes when a new edition is printed. (Minor
corrections and updates which are incorporated at reprint do not cause the date to change).
1st Printing - August, 1991
2nd Printing - November, 2004
Publication Number 984-06659
August, 1991
LI-COR, Inc. • 4421 Superior Street • Lincoln, Nebraska 68504 • 402-467-3576
FAX: [phone]
Toll-free 1-800-447-3576 (U.S. & Canada)
E-mail: [email protected]
www.licor.com

iii
TABLE OF CONTENTS
Section I. UNPACKING AND INITIAL INSPECTION
What's What............................................................................................................................................ 1-1
Optional Accessories .............................................................................................................................. 1-2
Section II. PRE-OPERATION
Set-up ...................................................................................................................................................... 2-1
Filling the Radiator.......................................................................................................................... 2-1
Filling the Condenser Block ............................................................................................................ 2-3
Power On ................................................................................................................................................ 2-4
Section III. OPERATION
General Description ................................................................................................................................ 3-1
Air Flow Through the LI-610.......................................................................................................... 3-1
Water Flow In the LI-610................................................................................................................ 3-2
Operation ................................................................................................................................................ 3-3
Command Input ...................................................................................................................................... 3-4
Analog Output ........................................................................................................................................ 3-4
Theory of Operation................................................................................................................................ 3-5
Ideal Gas Laws ................................................................................................................................ 3-5
Pure Water Vapor ............................................................................................................................ 3-6
Moist Air.......................................................................................................................................... 3-7
Pressure Effects ............................................................................................................................... 3-8
Temperature Effects ........................................................................................................................ 3-10
Relative Humidity............................................................................................................................ 3-10
Sample Calculations ........................................................................................................................ 3-11
Additional Relationships ................................................................................................................. 3-13

iv
Water Sorption................................................................................................................................. 3-13
Maximum Flow Rates...................................................................................................................... 3-13
Using the 610-03 Digital Pressure Meter................................................................................................ 3-16
Connecting the LI-610 and 610-03 to the LI-6200 RS-232C Port.......................................................... 3-18
References............................................................................................................................................... 3-20
Section IV. CALIBRATING LI-COR INSTRUMENTS
General Information ................................................................................................................................ 4-1
Calibrating the LI-6400 H2O Analyzer................................................................................................... 4-1
Setting the H2O Span....................................................................................................................... 4-1
Calibrating the LI-7000 CO2/H2O Infrared Gas Analyzer...................................................................... 4-4
Preliminary....................................................................................................................................... 4-4
Calibration Instructions.................................................................................................................... 4-6
I. Reference (Cell A) is Known and Constant ................................................................................ 4-7
II. Reference (Cell A) is Known, but not Constant......................................................................... 4-7
III. Calibrating for REM Operations............................................................................................... 4-8
User Calibration Example................................................................................................................ 4-10
Calibrating the LI-7500 CO2/H2O Infrared Gas Analyzer...................................................................... 4-12
Preliminary....................................................................................................................................... 4-12
Zero CO2.......................................................................................................................................... 4-14
Zero H2O.......................................................................................................................................... 4-14
Span CO2.......................................................................................................................................... 4-14
Span H2O......................................................................................................................................... 4-15
Calibrating the LI-840 CO2/H2O Infrared Gas Analyzer........................................................................ 4-16
Calibrating the LI-COR LI-6262 CO2/H2O Infrared Gas Analyzer ....................................................... 4-17
Preliminary....................................................................................................................................... 4-17
Absolute Mode H2O Zero Calibration............................................................................................. 4-18
Absolute Mode H2O Span Calibration ............................................................................................ 4-18
Differential Mode H2O Zero Calibration......................................................................................... 4-19
Precautions....................................................................................................................................... 4-19
Calibrating the LI-COR LI-1600 Steady State Porometer RH Sensor.................................................... 4-20
Initial Set-up..................................................................................................................................... 4-20
Calibration: Setting the Zero............................................................................................................ 4-21
Calibration: Setting the Span ........................................................................................................... 4-22
Check Intermediate Values .............................................................................................................. 4-23
Calibrating the LI-COR LI-6200 or LI-6000 Portable Photosynthesis System RH Sensor.................... 4-24
Precalibration ................................................................................................................................... 4-24
Calibration: Setting the Zero............................................................................................................ 4-26
Calibration: Setting the Span ........................................................................................................... 4-27

v
Check Intermediate Values.............................................................................................................. 4-28
Calibrating Relative Humidity Sensors (General) .................................................................................. 4-29
Calibrating Dew Point Hygrometers (General) ...................................................................................... 4-29
References............................................................................................................................................... 4-29
Section V. MAINTENANCE
Draining the LI-610 ................................................................................................................................ 5-1
Condenser Block.............................................................................................................................. 5-1
Radiator Assembly .......................................................................................................................... 5-2
Internal Air Filter .................................................................................................................................... 5-2
Internal Water Filter Screen.................................................................................................................... 5-3
External Fan Filter .................................................................................................................................. 5-4
Cleaning the Condenser Block................................................................................................................ 5-4
Fuses ....................................................................................................................................................... 5-5
Replacing the Air Pump Diaphragm....................................................................................................... 5-5
Recharging the 6200B Battery................................................................................................................ 5-7
Section VI. TROUBLESHOOTING
Appendix A. Specifications
Appendix B. Saturation Vapor Pressure Table
Appendix C. Psychrometric Charts
Appendix D. LI-610 Calibration Traceability
Warranty

Unpacking and Initial Inspection 1-1
Section I. Unpacking & Initial Inspection
What's What
Check the packing list included with your LI-610 to verify that you have
received everything that was ordered, and that you have also received the
following items:
Spare Parts Kit This bag contains replacement parts for your LI-610. As you become
familiar with the Dew Point Generator you will learn which items to
keep close at hand, and which items can be stored away.
Squeeze Bottle A 250 ml plastic squeeze bottle is included to aid in filling the radiator
assembly.
Syringe A plastic syringe is included to facilitate filling and draining of the
condenser block in the LI-610. Refer to Sections 2 and 5, respectively,
for complete filling and draining instructions.
Algicide A small bottle of liquid algicide is included, to prevent the formation of
algae in the radiator assembly of the LI-610. Refer to Section 2 for
complete instructions.
610-04 BNC millivolt
Leads
One set of millivolt leads terminated with a BNC connector is included
for connection to either the "Analog Output" or "Command Input"
fittings on the LI-610 front panel. See Section 3 for a complete
description of the function of these connectors.
610-01 AC Module 108-126/216-252 VAC, 48-66 Hz, for AC operation.

Section 1
1-2 Unpacking & Initial Inspection
Optional Accessories
Several optional accessories are available for use with the LI-610,
including:
610-02 Relative Humidity Calibration Accessories - for calibrating the
LI-6200 or LI-6000 Portable Photosynthesis System relative humidity
sensors, and the LI-1600 Steady State Porometer relative humidity sensor.
610-04 BNC mV Leads - for connecting to either the "Analog Output" or
"Command Input" fittings on the LI-610 front panel (one set included
with the LI-610). One set is included; a second set is required if you wish
to use the Analog Output and Command Input functions simultaneously.
6200B Rechargeable Battery (10.5 - 16 VDC). The 6200B Recharge-
able Battery is tested and fully charged before it leaves the factory, but
may discharge during shipping. It is a good idea to test your battery to
make sure that it is charged. If the battery is below 12 volts, it should be
charged before use. Refer to Section 5 for charging instructions. The
6200B requires the LI-6020 Battery Charger for recharging.
Never store batteries in a discharged state. Charge stored batteries
every three months.
LI-6020 Battery Charger (92-138/184-276 VAC, 47 to 63 Hz).
Battery Leads - for connection to a user-supplied battery (10.5-16VDC)
or other DC power supply.

Pre-Operation 2-1
Section II. Pre-Operation
Set-Up Two distinct systems must be filled with distilled (or deionized) water
before operating; the radiator assembly, located within the LI-610 case,
and the condenser block assembly, located externally.
Filling the Radiator To fill the radiator assembly, remove the black radiator fill cap on the top
of the LI-610 instrument case (Figure 2-1). The cap is not threaded, and
can be pulled straight up.
•Use the plastic squeeze bottle included with the LI-610 to add distilled
or deionized water to the radiator reservoir, until the water level is
visible in the fill tube.
•Connect the LI-610 to your power source (AC or battery).
•Turn the power switch ON. Turn the COOLER switch ON moment-
arily to flow water through the water pump and radiator assemblies.
Shut the LI-610 off and continue to fill the reservoir in this manner
until the water level remains visible in the fill tube. The radiator
assembly requires approximately 200 ml of water to completely fill to
this level.
☞TO PREVENT PERSONAL INJURY, DISCONNECT THE LI-610
FROM AC POWER WHEN FILLING THE RADIATOR
ASSEMBLY.
At this time, add 15-20 drops (2 ml) of algicide (included with the
LI-610) to the radiator reservoir. Replace the radiator fill cap.
If you plan to store the LI-610 in freezing conditions, drain the radiator
and condenser block assemblies completely. To operate the LI-610 in
freezing conditions, fill the radiator assembly (not the condenser) with a
mixture of ethylene glycol (one formulation of which is commonly called

Section 2
2-2 Pre-Operation
“antifreeze”). A 50/50 mixture of ethylene glycol/water will protect the
radiator from freezing to approximately -40 °C.
☞Ethylene glycol is the recommended antifreeze; do not use propylene
glycol or other antifreeze mixtures.
Radiator
Fill
Figure 2-1. LI-610 top view, showing location of radiator fill cap.

Section 2
Pre-Operation 2-3
Filling the Condenser
Block
The gold-plated condenser block assembly requires approximately 20 to
25 ml of distilled water to function normally. Follow these steps when
filling the condenser block assembly:
•Remove the plastic capnut located at the front left corner of the
condenser block assembly (see Figure 2-2). The condenser block can
now be filled using the 30 ml syringe included in your spare parts kit.
30cc
25
20
15
10
5
Syringe
Female
Luer
Lock
Bev-a-line
Tubing
Male
Luer
Lock
•Thread a female Luer lock (included in the spare parts kit) into the
syringe, and draw 20-25 ml of water into the syringe. Attach a male
Luer lock to the fill/drain port on the LI-610. Connect the two Luer
locks with a short section of 1/8” ID Bev-a-line tubing, as shown at left.
Fill/drain
port
Condenser
block
Figure 2-2. Location of the condenser block fill/drain port.
•Slowly add water to the condenser block; if the block is properly filled
the water level in the fill/drain tube will read midway between the
“Max” and “Min” marks on the condenser block ruler. Fill or drain to

Section 2
2-4 Pre-Operation
this level, as needed. If the condenser block is overfilled, simply use
the syringe to draw some water out of the fill/drain tube.
•Fill the syringe with air after filling the condenser block with water, and
syringe the air into the fill tube to remove any water which may adhere
to the side of the tube. This adhesion can cause a false water level
reading in the fill tube if it is not purged. Check the water level reading
in the fill/drain tube, and repeat, if necessary.
•After filling to the proper level, replace the threaded capnut.
It is recommended that the distilled water in the condenser block
assembly be changed every 2 days with continuous use.
The water level in the condenser should be monitored closely, particularly
if the temperature and water vapor content of the input air stream is
significantly different than the LI-610 set dew point. In this case, water
vapor will either condense out of the input air stream, thereby raising the
water level in the condenser, or evaporate out of the condenser into the
output air stream, lowering the condenser water level.
☞The condenser water may need to be changed more frequently if the
input air stream contains CO2at levels higher than 500 ppm. LI-COR
has found that high CO2levels cause the formation of precipitates within
the condenser block, which can cause the water to foam, leading to
unstable flow rates. If the rotameter gauge(s) fluctuates erratically, it
may be an indication that the condenser water needs to be changed.
Power On 1. The 6200B Rechargeable Battery and the 610-01 AC Module both fit
into the compartment on the back of the LI-610. Loosen the two
thumbnuts, and lift the right side of the retaining strap to access the
compartment. Place the 6200B in the compartment, and replace the
retaining strap. See Table 2-1 for the approximate battery life of the
6000B and 6200B batteries when used with the LI-610.
2. If you are installing the 610-01, remove the retaining strap. Install
the AC Module and replace the retaining strap. Tighten the thumb-

Section 2
Pre-Operation 2-5
nuts securely. Connect the power cord to one of the connectors
labeled 10.5-16 VDC on the rear panel.
Table 2-1. Hours of Battery Life for 6000B and 6200B Batteries
(@ 25 °C ambient).
Set Dew Point 6200B6000B
20 °C
10 °C
0 °C
Hours of Battery Life (approximate)
3.0-3.5
4.0-4.5
5.0-5.5
2.0-2.25
1.50-1.75
2.5-2.75
When the battery voltage reaches approximately 10.3 - 10.4 volts, the
LOW BATT light on the instrument front panel (Figure 2-3) will
illuminate, indicating that a system shutdown will occur if a charged
battery is not connected. Connect a fresh battery to continue
operation; the LOW BATT light will shut off. Instructions for
recharging the 6000B and 6200B batteries are given in Section 5.
The LI-610 will shut down when the battery voltage reaches
approximately 10 volts. The Peltier coolers, liquid pump, air pump,
fan, and display will turn off to conserve power. The LI-610 should
be turned OFF to prevent further battery discharge. Connect a fresh
battery, and if you haven't already done so, turn the LI-610 OFF and
back ON to reset the shutdown circuit. The LOW BATT light will
shut off, and normal operation will resume.
If AC line voltage is being used (with the 610-01 AC Module), make
sure the AC VOLTAGE selector on the AC module is set correctly
(choose the 115 setting for 108-126VAC, or the 220 setting for 216-
252 VAC), and plug the line cord into the AC receptacle.
WARNING! To prevent personal injury, never operate the LI-610 AC module if it
is not installed in the Dew Point Generator.
3. Turn the POWER switch on the front panel ON. The display will
show the temperature setpoint (TEMP SET), the actual temperature
(TEMP °C) of the condenser, or the battery voltage (BATTERY),

Section 2
2-6 Pre-Operation
depending upon the position of the function switch on the right side
of the display.
Turn the COOLER switch ON. The liquid pump will start circulating
water through the Peltier coolers and the radiator assembly. When
the AIR PUMP is switched ON and the FLOW ADJUST VALVE is
opened, the LI-610 will begin to generate an airstream with a dew
point temperature equal to the condenser temperature established
with the TEMP SET knobs.
Radiator
Fill Cap
ON/OFF Switch
Display
Low Battery LED
Temperature
Set Switch
Command Input
Temperature
Set Knobs
Flow Adjust
Valve
Analog Output
Rotameters
Air Output
Ports
Figure 2-3. LI-610 front panel.

Operation 3-1
Section III. Operation
General Description
The LI-610 Portable Dew Point Generator is a completely self-contained
instrument that is used to generate a moist air stream with a known dew
point.
A source of dry or ambient air is bubbled through a condenser block
assembly containing a water bath, whose temperature is precisely
controlled by a series of Peltier thermoelectric coolers. The internal
radiator and fan assembly dissipates the heat generated by the coolers,
providing a self-contained cooling system.
Water and air flow through two distinct paths within the LI-610 to
produce a moist air stream with a known dew point.
Air Flow Through
the LI-610
Air is drawn into the LI-610 through the AIR IN fitting on the instrument
back panel. Any impurities are removed from this air stream by a filter
before it reaches the air pump. Air leaving the pump passes through a
flow adjust valve on the instrument front panel, where the rate of air flow
through the LI-610 is controlled (see Figure 3-1).
The air stream then enters the two copper condenser blocks via the TO
CONDENSER fitting, where a bubbler stone is used to maximize the air-
to-water surface area, which ensures that air leaving the condenser blocks
is completely saturated with water vapor. Water vapor leaving the
condenser blocks through the FROM CONDENSER fitting is split into
two separate air streams, which are supplied to OUTPUT 1 and OUTPUT
2on the front of the instrument. The rate of flow through these outputs is
indicated by two rotameters on the front panel. Flow is divided between
the outputs using the flow control valve on output port #2.

Section 3
3-2 Operation
Two-Stage
Condenser
Peltier Cooler
ReservoirPumpRadiator
Cooling Water Path
Valve
PumpFilter
Air Inlet
Rotameter
Rotameter
Air Output
Port #1
Air Output
Port #2 Air Flow Path
Figure 3-1. Path of air and water flow through the LI-610.
Water Flow In
the LI-610
An internal radiator assembly is used in the LI-610 to provide a means
of dissipating the heat generated by the two Peltier coolers attached to
the condenser block (Figure 3-1).
The Peltier coolers are thermoelectric devices which absorb or liberate
heat, depending upon the direction of electrical current flow through the
junction of dissimilar metals.
When the coolers are switched ON, current flows in a direction which
causes heat to be absorbed or generated, based on the position of the
TEMPERATURE SET controls on the front panel, thereby lowering or
raising the temperature of the water present in the block. The condenser
blocks are copper, which is an excellent conductor of thermal energy. A
continuous flow of water between the coolers and the radiator allows
excess heat to be dissipated. A precision platinum Resistance-
Temperature-Detector (RTD) is used to monitor the temperature of the
condenser block (the condenser temperature is limited to +50 °C).

Section 3
Operation 3-3
☞If the temperature on the hot side of a Peltier cooler exceeds +65 °C, the
coolers will automatically shut down to prevent overheating. The
coolers will subsequently turn back on when the temperature drops
below this threshold.
Operation After filling the LI-610 with distilled water (Section 2), the instrument is
ready to begin generating a water vapor stream.
1. Turn the POWER switch ON. The display shows the temperature
setpoint (TEMPERATURE SET), the actual condenser block temp-
erature (TEMP °C), or the battery voltage (BATTERY), depending
upon the position of the function switch adjacent to the display.
2. Set the function switch to the TEMP SET position. Use the COARSE
and FINE TEMP SET knobs to set the desired dew point temperature
of the output air stream. The COARSE adjustment knob changes the
temperature set by large increments, and allows you to get close to
the desired set point very quickly. The FINE temperature adjustment
knob is then used to set the dew point precisely.
3. Set the function switch to the TEMP °C position, and turn the
COOLER switch ON. The Peltier coolers, liquid pump, and radiator
fan will turn on.
4. Turn the AIR PUMP switch ON. The air pump will turn on, starting
the flow of moist air out of OUTPUT 1 and OUTPUT 2. Use the
FLOW ADJUST knob to control the rate of air flow through the
LI-610. If you wish to shut off OUTPUT 2, simply turn the knob on
the rotameter above OUTPUT 2 clockwise until the flow is shut off,
and the rotameter shows zero flow.
☞Allow the LI-610 time to reach the desired dew point. The time required
will depend on the difference between the desired dew point temperature,
and the temperature of the cooling water used to remove heat dissipated
by the Peltier coolers. As an example, at 20 °C ambient air temperature,
the LI-610 will take approximately 10 minutes to reach a dew point of
0 °C, assuming that the cooling water temperature is also at or just above
20 °C.

Section 3
3-4 Operation
Command Input
The Command Input connector is used to provide a means of controlling
the temperature setting of the LI-610 from an external device (i.e., a
computer with an analog output board). One BNC connector with
attached millivolt leads is included for connection to this device.
The Command Input requires a 0 to 5 volt input; the corresponding
temperature set is linear, and is equivalent to 1 °C per 100 mV. For
example, an input signal of 3250 mV would produce a dew point
temperature output of 32.50 °C. The display will show the actual
temperature set point for the Command Input when the selector switch is
in the “Temp Set” position, regardless of what the knob setting is.
Connect the red lead from the BNC connector to the positive terminal of
the output device, and the black lead to the signal ground. The output
device must be able to supply 1 mA drive current. A source impedance
≤10Ωis required for an error ≤0.1%.
☞NOTE: The LI-COR LI-6400 Portable Photosynthesis System can be
configured to provide an analog output channel that controls the dew
point temperature of the LI-610. If both instruments are powered by AC
power, a "ground loop" can develop, in which there is more than one
ground connection path between the two pieces of equipment. Ground
loop-induced voltages cause unwanted signal noise that can affect the
operation of the LI-610. If you are using the LI-6400 and LI-610 in this
manner, we recommend that you isolate the two circuits by operating one
or both of the instruments with battery power.
Analog Output
The Analog Output connector is similar to the Command Input
connector, in that BNC millivolt leads are used to provide an analog
signal from the LI-610 to an external recording device. Analog output is
also linear (± 5 volts), and is equivalent to 1 °C per 100 mV.
Connect the red lead to the positive terminal of the readout device, and
the black lead to the signal ground. The readout device should have an
input impedance ≥100kΩfor an error ≤0.1% (the Analog Output
impedance is 100Ω).

Section 3
Operation 3-5
☞Detailed instructions for connecting the LI-610 to the LI-6200 Portable
Photosynthesis System are given on pages 3-16 to 3-19, along with a
discussion of the 610-03 Digital Pressure Meter.
Theory of Operation
Ideal Gas Laws When a gas stream passes through the LI-610 condenser, water vapor is
added or removed so that the exiting gas stream is saturated at the
condenser temperature. In most cases, that gas stream will be air, so we
shall consider a description of moist air.
Atmospheric gases at pressures near ambient conform closely to the ideal
gas law. The partial pressure of an ideal gas is given by
piV = niRT, 3-1
where pi is the partial pressure of gas component i {kPa}, V is volume
{m3}, niis the number of moles of gas component i, R is the universal gas
constant {0.008314 m3kPa mol-1 K-1}, and T is absolute temperature
{°K}. Dalton's Law of partial pressures states that the total pressure, P, of
an ideal gas mixture equals the sum of the component partial pressures.
For moist air,
P p p ... e
NO
22
=+++
or,
P = Σ pi + e 3-2
where Σ piis the sum of partial pressures of dry air components, also
expressed as Pa, and e is the partial pressure of water vapor. Therefore,
P = Pa+ e.
The partial pressure of water vapor may also be expressed as a mole
fraction. The mole fraction, X, of a component j in a mixture or solution
is defined as, Xj= nj/Σni. Combining equations (1) and (2) with the
definition of mole fraction, it can be shown that for an ideal gas mixture,
Xj= pj/P. Specifically, let w be the mole fraction for water vapor {mmol
mol-1}, then

Section 3
3-6 Operation
we
P
=1000 3-3
Pure Water Vapor The amount of water that can remain in the gaseous state at equilibrium
is limited. When pure water vapor is in stable equilibrium with a plane
surface of pure water or ice, with constant temperature and pressure at
the interface, it is said to be saturated. The partial pressure of pure water
vapor at saturation is a function of temperature alone, and is called the
saturation vapor pressure. Tabulated values of the saturation vapor
pressure of pure water vapor as a function of temperature based upon the
formulation of Goff and Gratch (1946) are given in the Smithsonian
Meteorological Tables (List, 1984).
Equations relating saturation vapor pressure to temperature based upon
those data are given by Lowe (1976) and LI-COR (1990). Lowe's
equation is a 6th order polynomial that gives accurate results (Table 3-1,
equation 3-11) and can be rapidly calculated on a digital computer.
However, it has the major disadvantage that it is easily applied in only
one direction, i.e., to compute vapor pressure from temperature. Given a
vapor pressure, it is difficult to solve Lowe’s equation for temperature.
Lowe's equation is used in the LI-6252 CO2Analyzer to compute vapor
pressure from a dew point provided by an external dew point hygrometer.
Equation 5-12 (LI-6262 CO2/H2O Analyzer Instruction Manual) of
LI-COR (1990) can be converted to the form: saturation vapor pressure at
temperature T, e(T) = a ×10[bT/(c+T)]. This equation (Table 3-1, equation
3-12) gives good accuracy from -50 °C to +50 °C, and can be solved for
either saturation vapor pressure, e(T) or temperature, T. It is used in the
LI-6262 to compute the dew point temperature from vapor pressure.