Alpha Moisture Systems dewTEC DS2000 User manual

dewTEC
DS2000 dewpoint meter
alpha moisture systems
alpha house, 96 city road
bradford, BD8 8ES
england
Tel: [phone]
Fax: [phone]
Email: [email protected]
Web: www.amsystems.co.uk
instruction manual

dewTEC DS2000 User’s Manual Page ii

dewTEC DS2000 User’s Manual Page iii
HOW TO USE THIS MANUAL
IMPORTANT: USER MUST READ THIS MANUAL BEFORE OPERATING THE
dewTEC DS2000 DEWPOINT METER
This manual comprises of six sections viz.
Section 1 General Description
Includes general description outlining the main features of the unit.
Section 2 Installation Instructions
Safety Information
Unpacking your dewTEC DS2000 and Moisture Sensor
Sensor Care
Sensor Installation
Dew Point Meter Installation
Electrical Connections
External AUTOCAL Control
Section 3 Operating Instructions
StartUp
Front Panel Display and Keys
Viewing Pre-Set Parameters
Alarm Settings
Resetting a Latched Alarm
Section 4 dewTEC DS2000 Settings
AUTOCAL
Factory Set Parameters
Calibration Data, Analogue Output Span, Offset, Filter, Serial
Communications, Display Colour, Lock, Help, Alarm Mode and
Direction, Analogue Output Type, Totaliser.
Section 5 RS485 Serial Communications
DataFormat
Protocol
Message Form
Section 6 Maintenance and Trouble Shooting
Maintenance
Problem Guide
Appendices Specifications and General Arrangement

dewTEC DS2000 User’s Manual Page iv

CONTENTS
HOW TO USE THIS MANUAL iii
1.0 General Description & Features 1
1.1 Description 1
1.2 Main Features 1
1.2.1 Dewpoint Meter Features 1
1.2.2 Sensor Features 1
2.0 Installation Instructions 2
2.1 Safety Information 2
2.1.1 Warning 2
2.1.2 Isolation 2
2.2 Unpacking your dewTEC DS2000 Dewpoint Meter and Sensor 2
2.3 Sensor Care 2
2.4 Installing the air/gas sampling system 3
2.5 Installing and commissioning the sensor 5
2.6 Installing your dewTEC DS2000 Hygrometer 6
2.6.1 Panel mounting cut out 6
2.6.2 Panel mounting 6
2.7 Electrical interface connections 6
2.7.1 Mains (line) supply 7
2.7.2 Sensor Connection 7
2.7.3 Alarm Relay Outputs 7
2.7.4 Linear (Analogue re-transmission) Output 7
2.7.5 Alarm Transistor Open Collector Outputs 7
2.7.6 Serial Communications Output 8
2.7.7 External Autocal Control 8
3.0 Operating Instructions 9
3.1 Start Up 9
3.2 Front Panel Display and Keys 9
3.3 Viewing Operating Mode Parameters 10
3.4 Setting the Alarms and hysterisis 11
3.5 Hysterisis Operation 12
3.6 Resetting a latched Alarm 12
4.0 Hygrometer Settings 13
4.1 Sensor Calibration (AUTOCAL) 13
4.2 Programmed Settings 14
4.2.1 Program Mode 14
4.2.2 Configuration Mode 16
5.0 Serial Communications 18
5.1 Data Format/Baud Rate 18
5.2 Protocol 18
5.3 Message Format 18
5.3.1 Message Form 1 18
5.3.2 Message Form 2 19
5.4 Error Conditions 19
6.0 Maintenance and Troubleshooting 20
6.1 Maintenance 20
6.2 Problem Guide 20
Appendices 22
Appendix A – Product Specification 22
Appendix B – General Arrangement 23
Document No. 1125 Issue 2 04/02/04
dewTEC DS2000 User’s Manual Page v

dewTEC DS2000 User’s Manual Page vi

1.0 General Description & Features
1.1 Description
The dewTEC DS2000 is a DIN style panel mounted dewpoint meter, designed to accurately
measure the dewpoint in gas or dry compressed air. The operating range of the unit is factory
set to the Moisture Sensor supplied with the unit. Process moisture value in factory set units
of °C, °F or PPM(V) is indicated, by the dewTEC DS2000 dewpoint meter, on a large five
digit seven segment display
The main external body of the Ultra High Capacitance Moisture Sensor is made of plated steel
and a stainless steel filter guard protects the sensing element within it.
The sensor can be located up to one kilometre away from the dew point meter.
1.2 Main Features
1.2.1 Dewpoint Meter Features
The dewTEC DS2000 dewpoint meter’s main features are:
• Display: Five large LED digits and one small LED digit, both with seven segments.
Two alarm status LED’s.
• User programmable LED indication to display in either Green or Red and can be
programmed to change colour when in alarm condition.
• Programmable via push button keys on front panel or PC (optional extra).
• Alarms: Two, independent, fully user programmable isolated relays with open
collector outputs. Programmable lock out to avoid unauthorised tamper.
• Displays maximum and minimum values.
• Displays elapsed time from alarm condition.
• Factory set calibration data in °C, °F or PPM.
• Factory set current (mA) OR voltage (mV) analogue output. Isolated and user
programmable to span over any range, within the overall range of the sensor.
• RS485 serial output with 1-99 address settings.
• 90 - 264V, 50/60Hz Universal input power supply.
• Accuracy ±2°C dewpoint (or equivalent in other moisture units).
• AUTOCAL feature for automatic calibration adjustment.
1.2.2 Sensor Features
The sensor main features are:
• Various dewpoint ranges available. Range ident on sensor packaging.
• Conditioned for long term stability.
• Can be located up to 1km from the dewTEC DS2000 dewpoint meter, connected by a
low impedance coaxial cable.
• ATEX Certified for use in potentially explosive areas with suitable Zener Barrier.
dewTEC DS2000 User’s Manual Page 1

2.0 Installation Instructions
2.1 Safety Information
Before installation please read the safety information below.
2.1.1 Warning
Suitably qualified personnel must install the equipment and care must be taken, as high
voltages may be present on the instrument terminals. The instrument must be mounted in a
position that provides protection behind the panel to at least IP20. Local regulations regarding
electrical installation should be rigidly observed.
2.1.2 Isolation
The power supply terminals and associated internal circuitry are isolated from all other parts
of the equipment, in accordance with EN61010-1, for connection to a category II supply
(pollution degree 2). Any terminals or wiring connected to the input or output, which is
accessible in normal operation, must only be connected to signals complying with the
requirements for Safety Extra Low Voltage (SELV) circuits.
Follow wiring instructions described later in this section.
2.2 Unpacking your
dewTEC DS2000 Dewpoint Meter and Sensor
Once unpacked, the items should be examined for any obvious external damage. Any
evidence of damage or mishandling should be notified to your carrier immediately.
The items should include dewTEC DS2000 dewpoint meter, Moisture Sensor packed in a
metal canister, instruction manual, sensor connecting cable and any optional extras if ordered.
The sensor is packed separately in a waterproof metal canister, with desiccant, to protect it
from excessive moisture exposure during transit. The sensor should be inspected for damage
then immediately stored in its canister until ready for installation. Retain the packaging for
future use, ensuring the sensor canister cap is tightly screwed to preserve the desiccant.
2.3 Sensor Care
Very special care must be taken not to damage the sensing element, for example by touching
or making any other physical contact, as this may damage the sensing surface and render the
Sensor useless.
Additionally, the following guidelines should always be followed:
• For any reason whatsoever DO NOT REMOVE THE SENSOR GUARD OR
ATTEMPT TO CLEAN THE SENSING ELEMENT WITHIN IT. The Sensor is
NOT user serviceable and does NOT contain any user replaceable parts. In the event
of a problem follow the problem guide at the end of this manual.
dewTEC DS2000 User’s Manual Page 2

• When not in use the sensor should always be stored in the desiccant contained metal
canister.
• The sensor should not be exposed to ambient conditions for considerably long periods.
• Exposure of the sensor to liquid water or condensing atmospheres should be avoided.
• The sensor should not be exposed to corrosive contaminants such as chlorine, ammonia
or mercury vapours. These gasses will gradually corrode the sensor and cause a loss of
sensitivity, hence affecting the system accuracy.
• Avoid heat sources and extreme temperatures when choosing installation site
• Ensure the sample gas exposed to the sensor is clean as contaminants such as oil, glycol
and heavy hydrocarbons can mask the sensing element, thus affecting the system
response. (If this is an issue contact your dewTEC DS2000 supplier for advice on a
suitable sample system.)
2.4 Installing the air/gas sampling system
The piping installation schematic diagram below shows all components, which could be used
in a dry gas measurement application although not all the items shown will be required for
every installation.
Care should be taken to ensure that the sample presented to the measuring sensor is not
contaminated with any component that will damage, contaminate or affect the sensor in a way
that will impair the system accuracy.
It is strongly recommended that the sample should not contain particulate matter, oil or other
heavy hydrocarbon condensate. If these components contaminate the sample system and/or
the measuring sensor, the system response time will be lengthened, although the sensor
calibration will not be effected.
The sample must not contain Ammonia, Chlorine, Ozone or any wet acid vapours or
liquid as these will permanently damage the sensor and impair calibration accuracy.
The flow rate, although not critical to the sensor measurement, should be low enough to avoid
abrasion to the sensor surface without being so low as to extend the system response time to
an unacceptable level. In general, a flow rate of between 2 and 3 litres/min at NTP will give
the right balance.
The sensor is a variable capacitor, which is directly affected by changes in partial pressure of
water vapour, and these changes, that are proportional to the dew/frost point temperature, are
displayed on the hygrometer display.
The measuring sensor can be installed directly into the process line but this does create
problems with access for maintenance and calibration. It is for these reasons that we
recommend that the sensor be installed in a bypass, fast loop or total loss sample system
where the sensor is accessible without interrupting the main process flow line.
dewTEC DS2000 User’s Manual Page 3

Piping installation Schematic
Notes
a. The sample point should be on the upper surface of the horizontal pipe, or f
a vertical section of pipe, wherever possible.
rom
b. The sample tube should run upwards from the sample point. If this is not
possible, then an inspection port or drain tap should be installed at the lowest
point in the sample system.
Main
Proces
s
Li
1
2
4
A
4B
5
6
8
1
0
1
1
P
9
7
3
Piping Schematic Component Index
1) Sample Isolation Valve - This is a recommended item as it allows access to the sample
system without interrupting the main process line.
2) Sample Tube – This should be stainless steel for dry air or gas applications but copper
or carbon steel can be used where wetter gases are to be measured. If any section of
the sample tube must be flexible then PTFE should be used. In most cases, 3mm OD
(1/8”) is sufficient as it provides good system response time within minimum flow.
6mm OD (1/4”) tube can be used where pressure drops across the 3mm tube are too
high
3) Filter Unit – A filter unit is recommended when the samples are likely to contain
particulate matter. If the air/gas sample contains heavy hydrocarbon condensate, the
filter must be of the coalescing type with a drain. The filter unit should be positioned
as close to the sample point as practical.
dewTEC DS2000 User’s Manual Page 4

4) Pressure Reduction Valve or Pressure Regulator – If the sample is to be measured at
atmospheric pressure then the valve 4A should be fitted and 4B omitted from the
system. If the sample is to be measured, at full line pressure and the exhaust vented to
atmosphere, then valve 4B should be fitted and 4A omitted from the system. If
measurements are to be taken at full line pressure and the sample is to be returned to a
part of the main line or a vent, which is at a pressure higher than atmospheric, and the
input to that line needs a controlled pressure then both 4A and 4B will be required.
5) Sample Pressure Gauge – This is not a critical part of the moisture measurement but
may be required if Dew/Frost point measurements are to be made at higher than
atmospheric pressure.
6) Measuring Sensor.
7) Sensor Holder.
8) Desiccant Chamber – This item is required when the sampling is to be intermittent.
When installed it prevents the ingress of wet air to the sample system, while the
sample is not flowing, improving the response time.
9) Flow Control Valve – This can be a separate item or combined with the flow indicator.
10) Flow Indicator – The recommended sample flow is 2 to 3 SL/M.
Sample Exhaust – The exhaust can be vented to atmosphere or returned to the process line as
discussed above.
2.5 Installing and commissioning the sensor
It is advisable to carry out an initial purge routine of the sample loop, before installing the
sensor, in order to remove the possibility of sensor damage on start-up.
Referring to the sample system schematic in section 3.4, open the inlet isolation valve slowly,
until a small flow of air/gas at atmospheric pressure flows through the inlet pipe work to the
sensor holder and exhausts through the sensor entry port of the sensor holder.
Allow this purge to continue for about 15 to 20 minutes to remove any residual moisture from
the sample pipe work and components.
Close the inlet isolation valve and install the sensor into the sensor holder. Securely push fit
the coaxial sensor cable connector in position on the sensor.
Open the inlet valve slowly, again and, by opening all valves after the sensor holder, allow a
low-pressure purge through the whole sample system. (Note. If a closed by-pass loop is
installed, this section of the procedure is not possible).
Set the required pressures and flows within the sample loop.
This completes the installation and commissioning but, on initial start-up, it could take several
hours for the system to reach equilibrium.
dewTEC DS2000 User’s Manual Page 5

2.6 Installing your
dewTEC DS2000 Hygrometer
The dewTEC DS2000 is a standard 1/8th-DIN size.
2.6.1 Panel mounting cut out
The panel on which your hygrometer is to be mounted must be rigid and up to 6mm thick.
The cut out size required is shown in the diagram below.
92.00mm
+0.5 | 0.0
2.6.2 Panel mounting
Your hygrometer is supplied with a panel gasket and push-fit fixing strap. Do not remove the
panel gasket, as this may result in inadequate clamping of the hygrometer in the panel.
Remove the push-fit fixing strap and place the hygrometer through the cut out from the front.
Then slide the fixing strap over the hygrometer housing from the rear of the panel until the
tongues engage in the ratchets and hygrometer is firmly in place.
2.7 Electrical interface connections
The rear terminal houses all connections to the unit. The connections are shown in the
diagram below and each input is described further in the following paragraphs. See the full
specification given at the end of this manual for more details on the interfaces.
13 14 15 16 17 18 19 20 21
12 22
11 23
10 24
987654321
N/O
COM
N/C
+
-
TOP
INTERNAL USE ONLY
N/O
COMN/C
RELAY 1
NPN
O/P1
COM
NPN
O/P2
ACOMB
RS485
COMMS
LN
POWER SUPPLY
90 - 264V
50/60Hz 7.5VA
Sensor
Connector
Relay Contacts
2A Resistive
110 - 240V ac
dewTEC DS2000 User’s Manual Page 6

2.7.1 Mains (line) supply
The hygrometer will operate on 90-264V AC, 50/60Hz mains (line) voltage. The power
consumption is 7.5VA.
An external fuse and a suitable switch or circuit breaker must protect the mains supply of the
hygrometer, which should be near the unit. Use a 1A antisurge Fuse.
13
14
L
N
Fuse 100-240Vac 50/60Hz - 1A antisurge
RECOMMENDED POWE R CONNECTION
If the relay outputs are to be used to carry mains (line) voltage, it is recommended that the
relay mains (line) supply should be switched and fused in a similar manner but should be
separate from the hygrometer mains (line) supply.
2.7.2 Sensor Connection
The sensor is connected to the hygrometer with the low impedance co-axial cable provided.
This low impedance cable may be up to 1 km long.
Note that the body of the sensor is not isolated. It is important that the earth potential at the
sensor is the same as that in the power supply earth to avoid stray pick-up. This is very rarely
a problem, but if in doubt, check for a voltage between the sensor body and the sensor holder
before installing the sensor.
2.7.3 Alarm Relay Outputs
The relay outputs of Alarm 1 and 2 are single pole double throw contacts rated at 2A resistive
at 120Vac or 240Vac, 50/60Hz.
The relay contacts are inherently isolated from the instrument and from each other.
2.7.4 Linear (Analogue re-transmission) Output
A 10-bit analogue signal representing the dewpoint is re-transmitted by the output, which is
factory preset to voltage or current output. The range of re-transmission can be set to
anywhere within the hygrometers’ operating range. See section 4 on how to set your options.
The output is isolated from the rest of the unit and should be wired using a twisted pair or
screened wire.
Load Impedance is 500Ωmaximum in mA ranges and 500Ωminimum in voltage ranges.
2.7.5 Alarm Transistor Open Collector Outputs
The open collector outputs of Alarm 1 and 2 are NPN outputs. The return is common for both
collectors.
dewTEC DS2000 User’s Manual Page 7

2.7.6 Serial Communications Output
The cable used should be suitable for data transfer at the selected rate (1200, 2400, 4800 or
9600) over the required distance. Transmitters/receivers conform to the recommendations in
the EIA Standard RS485.
The “A” terminal on the hygrometer (Terminal 17) should be connected to the “A” terminal
on the master device; the “B” terminal on the hygrometer (Terminal 16) should be connected
to the “B” terminal on the master device and the “Common” terminal on the hygrometer
(Terminal 18) should be connected to the “Common” terminal on the master device.
Where several hygrometers are connected to one master port, the master port transceiver in
the active state should be capable of driving a load of 120kΩper indicator. The masterport
transceiver in the passive state must have pull-up/pull-down resistors of sufficiently low
impedance to ensure that it remains in the quiescent state whilst supplying up to ±100µA each
to the hygrometer transceivers in the high impedance state.
2.7.7 External Autocal Control
An external autocal potentiometer can be added to control the setting remotely.
Connect a 20kΩmulti-turn potentiometer (20 turn or better) using a twisted pair or screened
cable between pins one and three. Wire the external potentiometer to increase resistance when
turned clockwise (Increasing the resistance will increase the display value).
Note, to use the external control, the internal control on the rear terminal needs to be turned
fully clockwise (see section 4).
1
2
3
T w i s t e dp a i ro r
s c r e e n e dc a b l e
20k
Ω
dewTEC DS2000 User’s Manual Page 8

3.0 Operating Instructions
This section covers day-to-day operation of the dewpoint meter.
3.1 Start Up
On power up, with the sensor connected, the unit will display the process value in dewpoint
(or PPM(v) if factory preset). Typical warm up time is 3 minutes.
3.2 Front Panel Display and Keys
Primary
Display
ON when
Alarm 1 is
active
ON when
Alarm 2 is
active
Secondary
Display
Down
key
Scroll
key
Program
key
Reset
key
Key / Display / Indicator Function
Primary Display
Normally displays the process Dewpoint/Moisture value. Operational programmed
parameters can be viewed by pressing the Programme key (P). The display will
indicate the parameter description for three seconds before showing the parameter
value. (Note: this function will only operate if the Help Facility is enabled - see
section 4, Dewpoint Meter Settings).
Secondary Display This single character identifier highlights the parameter value being displayed -
not lit when normally displaying the process Dewpoint/ Moisture value.
Down key ( ) In Edit Mode, decrements the flashing/blinking digit in the Primary Display.
Scroll key ( ) Puts the Dewpoint meter into Edit Mode. In Edit Mode this key selects the digit to
be altered in Primary Display - digit selected for alteration flashs/blinks.
Program Key (P)Selects parameter to be viewed/edited. In Edit Mode this key confirms edited
parameter value.
Reset Key (R)
When in normal display mode, pressing this key resets a latched alarm condition.
Also resets the Maximum (High) Value, Minimum (Low) Value or Alarm1
Elapsed Time, whichever parameter is displayed,
Down and Scroll Keys
() & ( )
When pressed simultaneously in Edit Mode, the unit will abort the Edit operation
and will restore the parameter to its initial value.
ALM 1 and ALM 2 LED Indicators lit (in all operation modes) when in alarm condition.
dewTEC DS2000 User’s Manual Page 9

3.3 Viewing Operating Mode Parameters
The flow diagram below shows the viewable parameters that are scrolled through as the
program key (P) is pressed:
PR
ALM1
ALM2
Model DS200 0 D EWPOINT METER
dew TE C
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METER
dewTEC
DEW POINT
PR
ALM1
ALM2
Model DS200 0 D EWPOINT METERdew TE C
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METERdewTEC
Maximum
(H igh)value
PR
ALM 1
ALM 2
Model DS2000 DEW POINT METERdewTEC
PR
ALM 1
ALM 2
Model D S2000 DEWPOINT METERdewTEC
Minimum
(L o w ) va lue
PR
ALM 1
ALM 2
Model DS2000 DEW POINT METERdewTEC
PR
ALM 1
ALM 2
Model D S2000 DEWPOINT METERdewTEC
Alarm 1
Elapsed Time
PRESS PRESS
PRESS PRESS
PRESS PRESS
PRESS PRESS
PR
ALM1
ALM2
Model DS2 000 DEWPOINT METERdewTEC
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METERdewTEC
Alarm 2
value
PR
ALM1
ALM2
Model DS2 000 DEWPOINT METER
dewTEC
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METER
dewTEC
PR
ALM1
ALM2
Model DS2 000 DEWPOINT METERdewTEC
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METERdewTEC
Alarm 1
value
PR
ALM1
ALM2
Model DS2 000 DEWPOINT METER
dewTEC
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METER
dewTEC
Alarm 1 H ysterisis
value
PR
ALM1
ALM2
Model DS2 000 DEWPOINT METERdewTEC
PR
ALM 1
ALM 2
Model DS2000 DEWPOINT METERdewTEC
Total
PRESS PRESS
PRESS PRESS
PRESS PRESS
PRESS PRESS
PRESS PRESS
Alarm 2 H ysterisis
value
NOTE: These displays
will not appear if the Help
function is disabled
Initial Display at Start Up. Displays your process
Dewpoint.
Maximum (High) Dewpoint since last reset. To reset,
press the (R) key when displayed.
Minimum (Lo) Dewpoint since last reset. To reset, press
the (R) key when displayed.
Accumulated time that Alarm 1 has been active since last
reset. This display format is in mm.ss up to 99 minutes
and 59 seconds, after which the format changes to
mmm.s. To reset, press the (R) key when displayed.
Dewpoint at and above which (Process High Alarm) or at
and below which (Process Low Alarm) Alarm 1 is active.
To set press ( ) when displayed and follow the
instructions given in paragraph 3.4.
Defines the width of the hysterisis band in dewpoint
applied on the ‘safe’ side of the Alarm 1 level. Set in the
same manner as Alarm value.
Dewpoint at and above which (Process High Alarm) or at
and below which (Process Low Alarm) Alarm 2 is active.
To set press ( ) when displayed and follow the
instructions given in paragraph 3.4.
Defines the width of the hysterisis band in dewpoint
applied on the ‘safe’ side of the Alarm 2 level. Set in the
same manner as Alarm value.
Total value based upon integration of the input signal
using the time base set in the hygrometer settings.
Automatic display change if there
is no key activity after 3 seconds
Display change due to key activity
dewTEC DS2000 User’s Manual Page 10

3.4 Setting the Alarms and hysterisis
Note, Alarm settings cannot be changed if the alarm LOCK is enabled in the hygrometer
program settings.
Edit mode for Alarm 1, Alarm 2 and hysterisis settings can be entered by pressing the scroll
key ( ) when the parameter is displayed. This is the first step shown in the flow diagram
below. Follow the rest of the steps shown in the diagram to set your required valve.
PR
AL M 1
AL M 2
PRESS
1 Select required alarm or
hysterisis parameter
display. See paragraph 3.3.
2
PR
ALM1
ALM2
PR
ALM1
ALM2
Left-most digit flashes
PR
AL M 1
AL M 2
PR ES S
3
PR
ALM1
ALM2
Use the Down key to change
value of flashing digit if required
PR
AL M 1
AL M 2
4
PR
ALM1
ALM2
Next digit flashes
PRESS
5 Repeat steps 3 and 4 for each digit required
6 When adjustment is
complete, confirm new
value by pressing (P). PR
ALM 1
ALM 2
PRESS
All digits will stop flashing
and new valve will be displayed.
Display is now back in operating mode
at the point where the setting mode was entered.
PR
AL M 1
AL M 2
PR
ALM 1
ALM 2
PRESS
To abort at any stage.
Note: if in edit
mode no key
activity occurs
for 90 seconds,
the hygrometer
automatically
returns to
operation mode
at the point
where the
setting mode
was entered
and cancels any
changes made.
dewTEC DS2000 User’s Manual Page 11

3.5 Hysterisis Operation
Operation of the hysterisis depends on whether the alarm is set to trip on high or low. The
diagram below shows how the hysterisis functions in each mode.
Alarm value
Alarm active
Alarm inactive
PROCESS
HIGH
ALARM Alarm Hysterisis
Alarm inactive
Alarm value
Alarm active
Alarm inactive
PROCESS
LOW
ALARM Alarm Hysterisis
Alarm inactive
Dewpoint
3.6 Resetting a latched Alarm
If Alarm 1 is configured to be a latching alarm relay when it is active, it can be reset as
follows:
1 Ensure Dewpoint is displayed
2 Press reset key (R)
Note, the latched alarm cannot be reset whilst the alarm condition persists.
dewTEC DS2000 User’s Manual Page 12

4.0 Hygrometer Settings
4.1 Sensor Calibration (AUTOCAL)
One of the most valuable advantages of the sensors is the Autocal feature.
The system relies on the fact that each sensor is designed to vice no further increase in reading
when it reaches its maximum moisture level. This means that the sensor will read its
maximum value when it is exposed to gas or air that is at that level and will continue to read
that value when it is exposed to wetter gas. The system can therefore be calibrated to the
analyser, on site, very simply by exposing the sensor to anything wetter than the maximum
level and adjusting the reading to the maximum dewpoint, on the hygrometer display, using
the Autocal Control on the hygrometer rear panel.
13 14 15 16 17 18 19 20 21
12 22
11 23
10 24
987654321
N/O
COM
N/C
+
-
TOP
N/O
COMN/C
NPN
O/P1
COM
NPN
O/P2
ACOMB LN
Sensor
Connector
Autocal
Control
Factory calibration is performed by comparing readings given from the hygrometer with
readings obtained from a primary standard, traceable to The British Standard moisture
generator held at the National Physical Laboratory. These comparative readings are taken
after the sensor has been set to automatic calibration and the results are shown in the
calibration certificate supplied with each sensor.
To autocal the sensor, follow these simple steps:
1. Disconnect the coaxial cable from the sensor. Remove the sensor from its normal position
so it is exposed to ambient air or hold in the palm of the hand if the sensor full range is
+20ºC dewpoint.
2. Leave the sensor for approximately five minutes (this time is not critical but the
hygrometer reading should be stable before any adjustment is made. It is not advisable to
leave the sensor exposed to ambient air for more than a few minutes as this will impair
dry-down when the sensor is re-installed).
3. IF NECESSARY, adjust the Autocal control, on the analyser front panel, until the display
indicates the maximum level for the sensor range in use.
dewTEC DS2000 User’s Manual Page 13

4. Disconnect the coaxial cable and re-install the sensor in its normal position. Reconnect the
coaxial cable.
This procedure re-confirms that the sensor is correctly calibrated to the hygrometer.
We recommend that verification of the overall linearity of calibration of the system should be
carried out on a 12 monthly basis.
4.2 Programmed Settings
The dewTEC DS2000 has two setting modes that modify the hygrometers’ operation. The
modes and parameters are shown in the following table:
MODE PARAMETER
Program Mode Calibration Data, Decimal Point Position,
Linear Output scaling, Offset, Filter,
Communications address and baud rate,
Display Colour, Lock, Help on/off
Configuration Mode Alarm Mode, Alarm Direction, Linear
Output type, Totaliser
Enter the mode that you require as described in this section to change a parameter.
NOTE: Many of the parameters are factory set during manufacture, test and calibration. Do
not change any of these settings as your hygrometer may give erroneous readings without you
knowing.
4.2.1 Program Mode
To enter Program Mode
(and to exit Program Mode)
Press and hold (P) for 3 seconds In program
mode, the secondary
display flashes continuously and
shows a single character, which
identifies the displayed parameter.
Once in Program Mode, follow these instructions to view and set parameters:
• Press (P) to scroll through the program mode parameters (as described in paragraph
3.3 for the operating parameters).
• To edit any displayed parameter, press ( ) to enter edit mode and ( ) to decrement any
digit (as described in paragraph 3.4 for setting the alarms).
dewTEC DS2000 User’s Manual Page 14