Michell Instruments S904 User manual

S904 and S904D
Humidity & Temperature Calibrator
User’s Manual
Data Acquisition
Desiccant Charge
Humidity = Yellow
De-Humidify - Green
Heating = Yellow
Cooling = Green
Chamber Set
Humidity
Chamber Set
Temperature
%rh °C
Auto On On Auto
Man. Off Off Man.
S-904
Humidity Calibrator
Max.
Min.
495 206
97209 Issue 3.1
October 2016

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© 2016 Michell Instruments
This document is the property of Michell Instruments Ltd. and may not be copied or
otherwise reproduced, communicated in any way to third parties, nor stored in any Data
Processing System without the express written authorization of Michell Instruments Ltd.
S904
For Michell Instruments' contact information please go to
www.michell.com

S904 & S904D User’s Manual
iv 97209 Issue 3.1, October 2016
Contents
Safety ................................................................................................................................vi
Electrical Safety ...........................................................................................................vi
Toxic Materials .............................................................................................................vi
Repair and Maintenance ...............................................................................................vi
Calibration...................................................................................................................vi
Safety Conformity ........................................................................................................vi
Abbreviations.....................................................................................................................vii
Warnings .......................................................................................................................... viii
1 INTRODUCTION ................................................................................................1
1.1 Description ........................................................................................................ 1
1.1.1 Comparison of the S904 and S904D ............................................................... 2
1.2 System Components ........................................................................................... 3
1.2.1 S904 ............................................................................................................ 3
1.2.2 S904D.......................................................................................................... 5
2 INSTALLATION ..................................................................................................7
2.1 Installing the Relative Humidity and Temperature Control Probe............................. 7
2.2 Filling the Water Reservoir .................................................................................. 9
2.3 Draining the Water Reservoir............................................................................. 10
2.4 Desiccant ........................................................................................................ 11
2.5 Power Supply ................................................................................................... 12
3 OPERATION ....................................................................................................13
3.1 Preparation ...................................................................................................... 13
3.1.1 Installing Relative Humidity Instruments for Calibration ................................. 13
3.2 Start-Up........................................................................................................... 14
3.3 Manual Control of Humidity and Temperature Setting.......................................... 14
3.4 Typical Response Times for Various Step Changes............................................... 14
3.5 Maximum Humidity Levels That can be Generated by the S904 Series .................. 15
3.6 25 pin D-sub Connector - S904.......................................................................... 16
3.7 Automatic Control of Temperature and Humidity Set Points - S904 ....................... 17
3.7.1 25 pin D-sub Connector - Rear Panel and Inside Chamber - S904D................. 18
3.7.2 S904D Example Wiring Diagrams ................................................................. 19
4 APPLICATION SOFTWARE - S904D ...................................................................21
4.1 Connecting and Starting the S904D Software .................................................... 21
4.2 LabVIEW®Software Menu Structure .................................................................. 22
4.2.1 Command - File .......................................................................................... 22
4.2.2 Command - Settings.................................................................................... 23
4.2.3 Command - Tools........................................................................................ 24
4.2.4 Command – Help ........................................................................................ 30
4.3 LabVIEW®Software User Interface .................................................................... 31
5 MAINTENANCE................................................................................................40
5.1 Troubleshooting................................................................................................ 40

S904 & S904D User’s Manual
Michell Instruments v
Figures
Figure 1 S904 .........................................................................................................2
Figure 2 S904D .......................................................................................................2
Figure 3 S904 - Front View.......................................................................................3
Figure 4 S904 - Back Panel ......................................................................................4
Figure 5 S904D Front panel......................................................................................5
Figure 6 S904D - Back Panel ....................................................................................6
Figure 7 Control Probe Installation............................................................................7
Figure 8 Location of Control Probe Inside the Climate Chamber ..................................8
Figure 9 Filling the Water Reservoir ..........................................................................9
Figure 10 Emptying the Water Reservoir ...................................................................10
Figure 11 Desiccant Replacement.............................................................................11
Figure 12 Level of Silica Gel Required .......................................................................11
Figure 13 Probe Ports ..............................................................................................13
Figure 14 Port Adapter Removal Tool ........................................................................13
Figure 15 Port Adapters and Removal Tool ................................................................13
Figure 16 Humidity and Temperature Setting Switches ...............................................14
Figure 17 25 pin D-sub Connector Location ...............................................................16
Figure 18 25 pin D-sub Connector ............................................................................16
Figure 19 Switches ..................................................................................................17
Figure 20 25 pin D-sub Connector ............................................................................18
Figure 21 S904D Wiring Diagram Example 1 .............................................................19
Figure 22 S904D Wiring Diagram Example 2 .............................................................20
Tables
Table 1 Typical Response Times for Step Changes ................................................... 14
Appendices
Appendix A Technical Specifications.............................................................................. 42
Appendix B EU Declaration .......................................................................................... 44
Appendix C Quality, Recycling & Warranty Information................................................... 46
C.1 Pressure Equipment Directive (PED) 97/23/EC ............................... 46
C.2 Recycling Policy .......................................................................... 46
C.3 WEEE Compliance........................................................................ 46
C.4 RoHS2 Compliance ...................................................................... 47
C.5 Warranty..................................................................................... 47
C.6 REACH Compliance ...................................................................... 48
C.7 Return Policy ............................................................................... 48
C.8 Calibration Facilities ..................................................................... 49
C.9 Manufacturing Quality.................................................................. 49
C.10 FCC (EMC Requirements for North America) .................................. 49
Appendix D Return Document & Decontamination Declaration........................................ 51

S904 & S904D User’s Manual
vi 97209 Issue 3.1, October 2016
Safety
The manufacturer has designed this equipment to be safe when operated using the procedures
detailed in this manual. The user must not use this equipment for any other purpose than that
stated. Do not apply values greater than the maximum value stated.
This manual contains operating and safety instructions, which must be followed to ensure the safe
operation and to maintain the equipment in a safe condition. The safety instructions are either
warnings or cautions issued to protect the user and the equipment from injury or damage. Use
qualified personnel and good engineering practice for all procedures in this manual.
Electrical Safety
The instrument is designed to be completely safe when used with options and accessories supplied
by the manufacturer for use with the instrument.
Toxic Materials
The use of hazardous materials in the construction of this instrument has been minimized. During
normal operation it is not possible for the user to come into contact with any hazardous substance
which might be employed in the construction of the instrument. Care should, however, be exercised
during maintenance and the disposal of certain parts.
Repair and Maintenance
The instrument must be maintained either by the manufacturer or an accredited service agent. Refer
to www.michell.com for details of Michell Instruments’ worldwide offices contact information.
Calibration
The internal reference probe (HT961T00) should be re-calibrated annually. The probe should be
returned to the manufacturer, Michell Instruments, or one of their accredited service agents for re-
calibration.
Safety Conformity
This product meets the essential protection requirements of the relevant EU directives. Further
details of applied standards may be found in the product specification.

S904 & S904D User’s Manual
Michell Instruments vii
Abbreviations
The following abbreviations are used in this manual:
°C degrees Celsius
°F degrees Fahrenheit
AC alternating current
DC direct current
max maximum
min minimum
% percentage
RH relative humidity
RS232 serial data transmission standard
T temperature
USB Universal Serial Bus
V Volts
mA milli Ampere

S904 & S904D User’s Manual
viii 97209 Issue 3.1, October 2016
Warnings
The following general warnings listed below are applicable to this instrument. They are
repeated in the text in the appropriate locations.
Where this hazard warning symbol appears in the following
sections it is used to indicate areas where potentially hazardous
operations need to be carried out.
DANGER
Electric
Shock Risk
Where this symbol appears in the following sections it is used to
indicate areas of potential risk of electric shock.

S904 & S904D User’s Manual
Michell Instruments 1
INTRODUCTION
1 INTRODUCTION
1.1 Description
The S904 Series are completely stand-alone and transportable calibrators for humidity
sensors, requiring no external services other than mains power. The calibrator is capable
of humidity generation over the range of 10-90% RH, with temperature control from
+10 to +50°C (+50 to +122°F). The calibration chamber features 5 interchangeable
ports to accommodate virtually any brand, type or model of sensor. This calibrator is
ideal for companies or organizations looking to calibrate large numbers of probes in a
laboratory or field setting.
The environment within the insulated calibration chamber is temperature controlled
using a 4-zone fan assisted Peltier arrangement for maximum stability, and minimum
temperature gradient. The humidity of the circulating air is precisely regulated using
a closed-loop control system that functions by proportionally mixing flows of dry and
saturated air.
Two highly visible LED panels display the current humidity and temperature within the
calibration chamber. The response time to a humidity or temperature step change is
typically less than 10 minutes, so a simple 3-point calibration can be carried out in
under an hour.
The S904 Series is easy to maintain. The desiccant changes color to indicate when it
needs to be recharged and this is visible through a clear window on the front of the
unit. Recharging the desiccant is simply a matter of heating it in a conventional oven
at +130°C (266°F) for 3 hours. The water reservoir at the front of the unit shows
the current saturator fill level, and makes it easy to top-up with distilled water when
required. The only external service required is a single phase power supply.
There are two versions available:
• S904
• S904D
With the S904D version, the humidity and temperature set points of the chamber can
be controlled with the supplied PC application software, enabling the operator to create
completely automated calibration profiles for unattended laboratory operation. The
software also gives the ability to monitor, chart and log data from the probes connected
to the S904D or application software for later analysis. Alternatively, the set points can
be controlled manually with the front panel controls - making the S904 Series ideal for
field calibrations where a PC is not available.

S904 & S904D User’s Manual
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INTRODUCTION
1.1.1 Comparison of the S904 and S904D
The S904D has the Data Acquisition connector on the rear panel, and a blanking plate
fitted to the front panel, as shown in Figure 2.
The S904D also features a USB, and an RS232 port on the rear panel, for communication
with the LabVIEW®application software.
Front Panel
Data Acquisition
Figure 1 S904
Figure 2
S904D

S904 & S904D User’s Manual
Michell Instruments 3
INTRODUCTION
1.2 System Components
1.2.1 S904
Front Panel S904
Data Acquisition
Desiccant Charge
Humidity = Yellow
De-Humidify - Green
Heating = Yellow
Cooling = Green
Chamber Set
Humidity
Chamber Set
Temperature
%rh °C
Auto On On Auto
Man. Off Off Man.
S-904
Humidity Calibrator
1 2 43 6
7
8
9
10
11
h
h
h
h
h
h
h
h
h
h
380 230
Max.
Min.
5
h
h
A A
B B
Figure 3 S904 - Front View
1. Chamber door
2. Water reservoir
3. Desiccant cell and indicator window
4. Relative humidity set point (% RH)
5. AManual/Auto switches for relative humidity / temperature control
MAN - Setpoint is set by switch 4 (humidity) and switch 6 (temperature)
AUTO - Remote control of relative humidity / temperature set points (see
Section 3.7).
BON/OFF switches for relative humidity / temperature control
6. Temperature setpoint (°C)
7. Humidity level indicator
8. Temperature level indicator
9. Humidity control indication LED
Humidify (yellow)
De-humidify (green)
10. 4-Zone chamber temperature control indication LEDs
Heating (yellow)
Cooling (green)
11. Data aquisition connector

S904 & S904D User’s Manual
497209 Issue 3.1, October 2016
INTRODUCTION
Back Panel S904
1
h
h
2
h
Figure 4 S904 - Back Panel
1. Ventilation fans
2. Electrical mains connector, on/off switch and power input fuse
Accessories
The S904 humidity and temperature generator is delivered with the following standard
accessories:
• Bottle of distilled water
• Desiccant cell filled with silica gel
• HT961T00 control probe
• Chamber door (according to customer specification)
• IEC mains cable
• Calibration certificate for internal reference probe
• Certificate of conformity (graph)
• User’s Manual

S904 & S904D User’s Manual
Michell Instruments 5
INTRODUCTION
1.2.2 S904D
Front Panel S904D
Data Acquisition
Desiccant Charge
Humidity = Yellow
De-Humidify - Green
Heating = Yellow
Cooling = Green
Chamber Set
Humidity
Chamber Set
Temperature
%rh °C
Auto On On Auto
Man. Off Off Man.
S-904
Humidity Calibrator
1 2 43 6
7
8
9
10
11
h
h
Max.
Min.
380 230
5
h
h
A A
B B
h
h h
h
h
h
h
h
Figure 5 S904D Front panel
1. Chamber door
2. Water reservoir
3. Desiccant cell and indicator window
4. Relative humidity set point (% RH)
5. AManual/Auto switches for relative humidity / temperature control
MAN - Setpoint is set by switch 4 (humidity) and switch 6 (temperature)
AUTO - Remote control of relative humidity / temperature set points (see
Section 3.7).
BON/OFF switches for relative humidity / temperature control
6. Temperature setpoint (°C)
7. Humidity level indicator
8. Temperature level indicator
9. Humidity control indication LED
Humidify (yellow)
De-humidify (green)
10. 4-Zone chamber temperature control indication LEDs
Heating (yellow)
Cooling (green)
11. Blind plate

S904 & S904D User’s Manual
697209 Issue 3.1, October 2016
INTRODUCTION
Back Panel S904D
23
1
45
h
h
h h h h
Figure 6 S904D - Back Panel
1. Ventilation fans
2. Electrical mains connector, on/off switch and power input fuse
3. Data acquisition connector
4. USB connection
5. RS232 connection
Accessories
The S904D humidity and temperature generator is delivered with the following standard
accessories:
• Bottle of distilled water
• Desiccant cell filled with silica gel
• HT961T00 control probe
• Chamber door (according to customer specification)
• IEC mains cable
• Calibration certificate for internal reference probe
• Certificate of conformity (graph)
• User’s Manual
• USB cable
• LabVIEW®software

S904 & S904D User’s Manual
Michell Instruments 7
INSTALLATION
2 INSTALLATION
Before using the S904 Series, make sure that Sections 2.1, 2.2
and 2.4 are read thoroughly.
The S904 Series’ enclosure is designed for bench top mounting in a laboratory type
environment. It must be positioned in a clean and level location with sufficient clearance
at the rear of the enclosure for adequate ventilation.
The S904 Series is not designed to be fully portable. However
it can easily be moved to any suitable location for use. Before
moving ensure that any water in the reservoir is drained and the
relative humidity control probe in the chamber is removed.
The S904 Series should NOT be moved while in operation.
2.1 Installing the Relative Humidity and Temperature Control Probe
The HT961T00 Relative Humidity and Temperature Control Probe is supplied as an
accessory with the S904 Series. This control probe is removed during transportation.
To install the control probe remove the chamber door and plug in the probe as shown
in Figure 7.
This internal control probe is delivered with its own calibration certificate.
Control Probe 
Figure 7
Control Probe Installation
The chamber control relative humidity and temperature probe
must always be removed during transportation.

S904 & S904D User’s Manual
897209 Issue 3.1, October 2016
INSTALLATION
GND
OUTPUT TEMP
+ SUPPLY (8 - 35 VDC)
OUTPUT RH
BOTTOM VIEW
TOP VIEW
Control
Probe
Connector
Figure 8 Location of Control Probe Inside the Climate Chamber

S904 & S904D User’s Manual
Michell Instruments 9
INSTALLATION
2.2 Filling the Water Reservoir
Before operation the water reservoir located on the front panel must be filled with
distilled water (supplied with the instrument).
Do not use tap water or demineralized water!
Figure 9 Filling the Water Reservoir
Use the bottle supplied to fill the water reservoir.
1. Remove the red plastic cap from the top of the reservoir.
2. Carefully fill with clean distilled water to a level between the two indicator
lines.
3. Replace the red cap on the water reservoir after filling.
Do NOT fill above the MAX indicated line as this may cause liquid
to enter the humidity chamber and adversely affect the control
process.

S904 & S904D User’s Manual
10 97209 Issue 3.1, October 2016
INSTALLATION
2.3 Draining the Water Reservoir
Drain the water reservoir before transporting, or if the system is accidentally overfilled.
To empty the water reservoir:
1. Remove the red caps from the bottom and top of the water reservoir.
2. Drain the water into a suitable container.
3. Tilt the instrument to empty the reservoir completely.
4. Re-fit the red cap after emptying.
Figure 10 Emptying the Water Reservoir
It is essential to drain the water reservoir before transporting or
when the system is not going to be used for a few weeks.
Do not re-use any of the drained water within the system.

S904 & S904D User’s Manual
Michell Instruments 11
INSTALLATION
2.4 Desiccant
The S904 Series has a container filled with a desiccant which is used to dry the air.
Figure 11 Desiccant Replacement
The desiccant container can be accessed by following these steps:
1. Remove the clear plastic screw cap on the front panel.
2. Pull out the desiccant container using the finger tips.
3. Fill with desiccant up to the thread as shown in
Figure 12 below.
Figure 12 Level of Silica Gel Required
The natural color of the desiccant (dry silica gel) should be orange, or blue (depending
on type). As moisture is absorbed, the color will gradually change to transparent or
pink (depending on type). When the desiccant has become transparent or pink - this
is an indication that the instrument’s ability to generate low humidity is reduced. It is
recommended that the silica gel is replaced or regenerated at this time.
The desiccant can be regenerated by emptying it completely from the desiccant chamber
and drying it in an oven for approximately 3 hours at a temperature of +130°C (266°F).
After drying it in an oven, allow the desiccant to cool before refilling the desiccant
chamber and refitting the chamber into the generator. Ensure that the screw lid is
correctly fitted.
Frequency of desiccant regeneration or replacement is dependant entirely upon the
length of time in operation. Typically, given a normal calibration profile and operation
cycle, the S904 Series can continually generate accurate and stable chamber humidity
for a period of several weeks before regeneration or replacement of the desiccant is
necessary.

S904 & S904D User’s Manual
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INSTALLATION
2.5 Power Supply
A single mains power supply between 100 to 240 V AC is required to operate the unit.
The power supply connection is a 3-pin IEC plug located on the rear panel of the
instrument. The ON/OFF switch and the power input fuse are in the same location,
adjacent to the power socket.
A 3-core power cable is provided.
DANGER
Electric
Shock Risk
The instrument must be connected to an electrical earth for
safety purposes.