Shaw SADP Operating Instructions Manual

SADP_Operating_ Instructions_0114

Model SADP

Automatic Dewpoint Meter

Operating Instructions

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SADP_Operating_ Instructions_0114

Unpacking your
Shaw Moisture Meters Model SADP

Please examine the SADP package for any damage or mishandling. If any
damage is evident please notify the carrier and the Shaw Moisture Meters
representative from where this unit was purchased.

You should have received (if ordered):

 1 Model SADP Instrument
 1 Carry Case
 1 Screwdriver & Allen Key
 1 Instruction Manual
 1 Pressure Dewpoint Circular Calculator
 1 2m length of PTFE tubing

If anything is missing please contact your distributor immediately.

SADP_Operating_ Instructions_0114

Index

Contents Page

1.0 General Description 1

1.1 Ranges 1

2.0 Safety Information 2

2.1 Hazardous Area Use – Safety Information 2

2.2 Pressure Exposure 2

3.0 Installing the Air / Gas Sampling System 3

3.1 Gases to Avoid 3

3.2 Piping Installation Schematic 4

3.3 Piping Schematic Component Index 4

4.0 Purging the Sample Connection 5

4.1 Sample Connections 5

5.0 Controls 5

6.0 Normal Operation 6

7.0 Calibration Checking 7

8.0 The Sensor 8

8.1 Gaining Access to the Sensor 8

9.0 Additional Information 9

9.1 Anti-Static Sample Case 9

9.2 Desiccant and Head Seal 9

9.3 Batteries and Battery Check 9

9.4 Temperature 10

9.5 Pressure 10

9.6 Response Time 10

9.7 Guarantee 10

10.0 Basic Definitions 11

11.0 Electrical Function Check 12

12.0 Problem Guide 13

13.0 Hygrometric Equivalents 15

14.0 SADP Specifications 16

SADP_Operating_ Instructions_0114

1.0 General Description

The SADP & SADP-TR are battery operated portable dewpoint meters designed for spot checks or

continuous use. The instrument provides direct indication in dewpoint temperature and parts per million
on a 12cm analogue scale. SADP-D versions perform the same function but display only Dewpoint on a
LCD display.

The instrument may be used to give a continuous reading as long as sample gas is flowing through the

test chamber [head] of the instrument, a reading will be given of the gas moisture content. Alternatively
results are obtained in a few minutes when making spot checks.

The SADP instrument is operated with its own internal batteries and requires no external power source.

The instrument comes supplied with 6 “c”-size cells. In normal operation these will last for over 12
months.

The unique measuring head is designed to keep the sensor dry when the instrument is not in use,

making spot checks a simple and speedy process with minimum air or gas usage.

The SADP is provided as standard with a padded carrying case with shoulder strap, a moisture

calculator, a screwdriver for the Automatic Calibration control, a special key for the security plate
covering the battery carriers, and a 2 meter length of flexible PTFE (Teflon) sample pipe.

The instrument is certified for use in hazardous areas (Ex ia IIC T6 Ga).

1.1 Ranges

SADP-(r): Range

Purple (P) -100 to 0 deg.C DP, 0-6000 PPM.
Silver (S) -100 to -20 deg.C DP, 0-1000 PPM.
Red (R) -80 to -20 deg.C DP, 0-1000 PPM, 0-10 on TR version.
Grey (G) -80 to 0 deg.C DP, 0 - 6000 PPM, and 0-10 on TR version.
Blue (B) -80 to +20 deg.C DP, 0 - 23,000 PPM, (manual-cal)

SADP_Operating_ Instructions_0114

2.1 Hazardous Area Use – Safety

All SADP Shaw Automatic Dewpoint meters are certified Intrinsically Safe as a standard feature.
They must be fully assembled to meet the certification requirements, i.e. they must not be switched on

in a hazardous location if any component is missing or removed. E.G. battery cover plate or sensor
head assembly etc. This instrument is only certified Intrinsically Safe to T6 with the use of Varta 3014
long life batteries as supplied.

Certification: ATEX Coding -

II 1G

Ex ia IIC T6 Ga (Ta = – 20ºC to +40ºC)

FM Coding - CLASS I, ZONE 0 AEx ia IIB+H2 T6

It is the responsibility of the user to ascertain the suitability of the SADP for use in hazardous areas.
Risk assessments should be performed prior to use, taking into account the SADP certifications, the
location and the gas being monitored etc.

The USA certification is to CLASS I, ZONE 0 AEx ia IIB+H2 T6, which effectively means that the

instruments may be used in any environment except a deep mine.

The ATEX certification is Ex II 1 G Ex ia IIC T6 Ga. This means:-

Ex-European certification mark for electrical equipment for use explosive atmospheres
II -Areas classified hazardous due to presence of flammable gases or vapour
1 -Areas classified as Category 1 Risk according to the ATEX Directive (equates to Zone 0)
G -Risk due to presence of flammable gases or vapours according to the ATEX Directive
Ex ia - Intrinsic Safe
IIC - suitable for use with all classes of gasses and vapours
T6 - the product has a maximum surface temperature of 85°C (in an ambient temperature range of -

20°C to + 40°C) and can be used with any gases or vapours which have an ignition temperature above
this.

Ga - EPL (Equipment Protection Level) marking

2.2 Pressure Exposure

The maximum pressure to which the telescopic measuring head is exposed

must not be more than

0.3barg, 4.35psig, 30kpag or 0.3kg/cm2g

Exposing the measuring head to higher pressures may damage the instrument

and result in injury to the operator or other personnel in the area

SADP_Operating_ Instructions_0114

3.0 Installing the Air/Gas Sampling System

The piping installation schematic diagram (see section 3.2) 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 SADP is not contaminated with any

component that will damage, contaminate or affect the SADP in a way that will impair the unit’s
accuracy.

It is strongly recommended that the sample should not contain particulate matter, oil, hydrocarbon or

any other condensate. If these components contaminate the sample system and/or the measuring
sensor, the SADP response time will be lengthened, although the sensor calibration will not be effected.

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 SADP response time to an unacceptable
level. In general, a flow rate of between 5 and 8 litres/min at NTP will give the right balance.

The sensor used in the SADP 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 instrument indicator.

3.1 Gases to Avoid

The moisture sensors are suitable for many different industrial and research applications. Most gases
can be checked for their moisture content with no need for the calibration to be altered when changing
between different gases, as the sensor operates only with reference to the water vapour content. There
are, however, some gases that must be avoided, as they are not compatible with the material of
construction of the sensor. Ammonia (NH

3

), Ozone(O3) and chlorine (Cl) must be avoided at all times,
even in small quantities. Hydrogen chloride (HCl) also attacks the sensors very quickly. Some, less
aggressive, acidic gases, such as sulphur dioxide (SO

2

), can be monitored, as long as the moisture

content is low, generally less than 100ppm(v). If in doubt, please ask your supplier.

Sulphur hexaflouride (SF

6

) has no effect on the sensor. If the gas has been exposed to arcing,
however, it is possible that various acidic species will have been formed that will corrode the sensor.
When testing SF

6

that may have been arced, therefore, an acidity test should be carried out first; if the

gas proves to be acidic then the moisture test should not be carried out.

SADP_Operating_ Instructions_0114

3.2 Piping Installation Schematic

3.3 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 with 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.

4. Pressure Reduction Valve or Pressure Regulator – the sample is measured at atmospheric

pressure requiring that valve 4 is fitted to the system.

5. Flow Control Valve – This can be a separate item or combined with the flow indicator (8).

6. Sample Connection

7. SADP.

8. Flow Indicator – The recommended sample flow is 5 to 8 L/M.

9. Sample Exhaust – The exhaust is vented to atmosphere or returned to an atmospheric pressure

line.

1

2

3

4

5

6

7

8

Main

Process

Line

Notes

a. The sample point should be on the upper surface of the horizontal pipe, or from a

vertical section of pipe, wherever possible.

b. The sample tube should run upwards fr om 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.

9

SADP_Operating_ Instructions_0114

4.0 Purging the Sample Connection

Refer to the sample system schematic in section 3.2.

It is advisable to carry out an initial purge of the sample loop, before connecting the
SADP, in order to avoid the possibility of sensor damage on start-up.

Open the sample isolation valve (1) slowly, until a there is a small flow of air/gas at atmospheric

pressure from the pressure reduction valve (4) into SADP line. Allow the air/gas to exhaust through the
sample connection (9).

The SADP is not flow sensitive however the sample flow needs to be enough to purge the sensor head

effectively, so anything less than 1 litre/min would mean that the instrument would take too long to
settle to a stable reading. The flow should also not be so high that the gas velocity could physically
damage the sensor or cause backpressure in the sensor head, so should not exceed about 8 litres/min.

Allow this purge to continue for 2 minutes to remove any residual moisture from the sample pipe work

and components. Check that no liquid or particulate contamination, which could damage the sensor, is
passing through the sample pipe. Directing the sample onto a piece of white paper (such as a filter
paper) will make it easier to see any dust or oil mist in the sample.

4.1 Sample Connections

The SADP instrument is supplied with push-on sample connections on each side of the test chamber

(head) of the instrument. These connections are reversible and flow direction is not important. The
fittings are designed for pipe having an internal bore of approximately 6mm (1/4"). Only the PTFE
(Teflon) pipe provided should be used, as other materials are unsuitable. The sample pipe should be
heated in a naked flame for a few seconds before being pushed onto the instrument connection for the
first time. This will provide a good gas-type connection and ensure accurate results.

5.0 Controls

SADP instruments have a single rotary switch to the right of the indicator, which controls the power

supply, the battery check and the range selection (in dual range models) . The switch positions are
marked on the instrument fascia. SADP-D models have a single on/off switch.

SADP_Operating_ Instructions_0114

6.0 Normal Operation

Brief operating instructions will be found on the label fastened to the top of the instrument cabinet. The

standard test procedure is as follows:

1. Switch the instrument on, and check the battery condition.

2. At the sample point to be tested open the sample valve or regulator slightly and check that no dirt or

condensate is expelled. [If any dirt or condensate is present, wait until it is cleared, or abandon the
test].

The pressure of the sample source is not important: however the instrument needs a small sample

of the air or gas which has been reduced to atmospheric pressure at the sample point (It must
not exceed 5 PSI for safe operation) - easily achieved by opening the valve just enough to allow a

small flow to escape through the dewpoint meter.

3. Connect the PTFE sample pipe supplied with the instrument between the sample tapping point and

the instrument, using either of the connections of the head/sensor assembly.

4. Adjust the sample valve or regulator to give a gentle flow through the instrument, [5/10 L/min. is

ideal — but the flow rate is not particularly critical. Do not exceed a flow of about 20 L/min].

5. Allow the sample to flow for 2 or 3 minutes in order to purge the sample pipe (a longer time might be

needed if testing very dry gas - drier than about -65 c. dewpoint). Then place a finger over the outlet
connection of the instrument head, and the sample pressure will cause the head to open. Remove
finger from the instrument when the head is fully open. [If there is insufficient sample pressure, fit a
length of 1 or 2 metres of flexible pipe to the outlet connection of the instrument head, and slowly
raise the head by hand].

6. The instrument reading will move up the scale (wetter), and stabilise. When there is no further

change in reading, note the result. If the reading moves up the scale (wetter) and then moves down
the scale (drier) then either the sample pipe was not purged enough before the head was raised, or
the sample is becoming drier during the test. (Perhaps by taking the sample from a pipe in which the
gas has been stagnant for some time).

If in doubt about the suitability of the sample flow rate, or the materials of the sample pipe being used,

increase the sample flow rate after the final reading has been obtained. If the instrument moves to a
drier reading this indicates that the original flow rate was too low, or that there is a leak in the system
allowing ambient moisture into the sample, or that the sample pipe is still wet.

7. After the test is complete, and if continuous reading is not needed, close the instrument head ready

for the next test.

8. Note these instruments are designed for rapid moisture determination when operated from Dry to

Wet, in this case they should give a 95% step change within 30 seconds. When operated Wet to Dry
we cannot quote any response time as this is dependant upon many variables but will be
considerably longer than the Dry to Wet response time.

Dual Range Model TR

This model should be operated in the same way as the standard range model except that when the
reading has stabilized you can move the switch from STD RANGE to LOW RANGE. This will activate
the lower red scale marked WATER VAPOUR. This is simply an amplification of the middle green
scale marked PPM (V) and will display a more accurate reading between the range of 0-10ppm.

PLEASE NOTE: When performing the Automatic Calibration procedure the switch must be returned to

the STD RANGE position.

SADP_Operating_ Instructions_0114

7.0 Calibration Checking

When Shaw invented the capacitance sensor many years ago it was a real breakthrough. The second

major breakthrough came when we introduced the unique Automatic Calibration System for our
sensors.

This is a major advantage of the Shaw measurement system. No other instrument can be checked so

easily and quickly.

The system relies on the fact that each sensor is designed to give no further increase in reading when it

reaches its maximum moisture level. This means, for example, that the Grey Spot sensor used in the
Model SADP-G for the range -80 to 0 C dewpoint will read 0 deg C when exposed to gas at 0 deg C
dewpoint, but will continue to read 0 deg C dewpoint when it is exposed to wetter gas. The system can
therefore be calibrated very simply by exposing the sensor to anything wetter than 0 deg C dewpoint,
and adjusting the reading to that point on the dial. In practice there is not an immediate cut-off, and the
0 deg C dewpoint mark on the dial will be found at about 3 deg below the Automatic Calibration line.
This enables the instrument to retain the maximum possible accuracy throughout its range.

In practice, the instrument’s calibration is checked as follows:

AUTOMATIC CALIBRATION - All Models Excluding SADP-Bl

1. Ensure that no gas sample is connected to the instrument head connections. Switch meter to

Read, or Standard range if a TR Model. Switch to On for SADP-D models.

2. Raise the head of the instrument by hand and pump it up and down a few times, ending in the

raised position.

3. After about 1 minute (not critical, but not more than a few minutes) check the instrument reading.

On SADP models it should be at the Automatic Calibration line. It is not critical within 1 or 2
degrees. N.B. Extremes of humid or dry room air conditions may affect the reading slightly - see
below. SADP-D models must be set to the Wet limit of the sensor.

4. If the reading requires adjustment locate the Automatic Calibration control, which is to be found

on the front panel of the instrument, and using the small screwdriver provided, turn the control
clockwise to increase the reading (wetter) or anti-clockwise to decrease it.

5. Close the instrument head.

NOTE: When the outside temperature is below 0 deg C or in an Air-Conditioned environment the room

dewpoint may also be below 0. Under these conditions we suggest that an independent check of the
room dewpoint be made against which the calibration can be set or, more easily, assume that the room
dewpoint temperature is the same as the outdoor air temperature. This will be quite sufficient except in
very unusual weather conditions.

MANUAL CALIBRATION - Models SADP-Bl and SADP-D-Bl

The wide range of the Model SADP-Bl and SADP-D-Bl means that very rarely will the room air dewpoint

be above the maximum of the range. This means that true Automatic Calibration will not work. To
overcome this, simply use a wet & dry bulb hygrometer, or similar, to determine the room air dewpoint
temperature, and at stage (4) above set the reading to the actual air dewpoint. There is, of course, no
Automatic Calibration line on these meters.

We suggest you check the automatic calibration a minimum of two to three times each year, and that

annually the instrument is returned for a full range calibration check

SADP_Operating_ Instructions_0114

8.0 The Sensor

The Shaw High Capacitance Sensor has been undergoing continuous development since it was

invented by Mr. J. L. Shaw in the late 1940’s. Protected by world patents the sensor is manufactured by
a unique automated process, which results in a long life device with fast response, high accuracy and
good stability.

Construction of the sensor starts with an ultra-high purity aluminium wire, which is coated with a

hygroscopic layer and finally covered by a film of porous gold. The gold film and the aluminium core
form the plates of the capacitor. The capacitance value, and the change in capacitance over the
measuring range of each sensor is many times greater than any other device, resulting in a system
which can operate at low frequency [50 or 60Hz] without any risk of interference or pick-up from
external cables or other sources.

Some of the water vapour molecules in the atmosphere surrounding the sensor will enter the dielectric

layer where, due to the extremely small size of the pores, their Brownian motion will be limited, their
energy will consequently be reduced and they will condense into liquid water. Due to the very high
dielectric constant of water [about 80] compared with the other vapours which may be present, this
produces a marked change in the dielectric value of the sensor which is then measured by the
analyser. A dynamic equilibrium will exist between the water vapour outside the sensor and the
condensed water within the pores. This equilibrium is maintained, and the response time of the sensor
can generally be considered to be at least as quick as the system into which it is installed.

Molecules larger than water vapour [one of the smallest gas molecules] cannot enter the pores, making

the sensor resistant to many contaminants and specific to water vapour pressure regardless of the
carrier gas. Even molecules such as Hydrogen which may enter the pores, have such a low dielectric
constant, and will not condense, and so cannot interfere with the reading.

This is a feature unique to the Shaw sensor. All other sensors of the capacitance type are affected by

molecules such methanol which cause great inaccuracy.

8.1 Gaining Access to the Sensor

The sensor is mounted inside the test chamber (head) of the instrument, and is accessible by

removing the test chamber from the instrument as follows:-

1. Undo the three screws in the base flange of the head assembly and lift the complete head

off the instrument. Pull out the plug from the sensor.

2. Using a 22mm A/F wrench, unscrew the sensor from the head assembly. Do not leave the

head without a sensor fitted for more than a few minutes, as the desiccant will absorb
moisture from the room air.

3. When refitting the sensor, push the coaxial plug in firmly and don't forget to fit the brass

spacer.

SADP_Operating_ Instructions_0114

9.0 Additional Information

9.1 Anti-Static Carrying Case

The carrying case supplied with the SADP is manufactured from anti-static material. The SADP unit can

be fully operated within the carrying case. It is recommended that the SADP is left in the carrying case
whenever in the hazardous area.

9.2 Desiccant and Head Seal

The sensor is kept dry when not in use by the desiccant contained in the head assembly. In the Model

SADP this is designed to maintain the sensor at about -75 C dewpoint, many years’ experience has
shown that this maintains the optimum responsiveness of the sensor.

The above readings should be obtained when the instrument has been left with the head in the closed

position for a few hours - e.g. overnight. As the desiccant only has to dry a very small volume of air or
gas after each test, and is completely isolated from the test gas and the room air, it has a life of
approximately 5 years in normal use. After very long service, or in case of accident the desiccant can
easily be replaced as follows:

1. Grasp the black plastic ring (Head Seal), which separates the inner and outer sections of the head
assembly, and unscrew it until it can be removed. Pull the inner section out of the outer section. In

the case the Head Seal requires Replacement slide the old seal off noting the orientation and place

the replacement on a firm bench upside down (threads uppermost. Now insert the head into the
seal, and when it meets the seal push firmly till it passes the seal.

2. Unscrew the plain brass base of the inner section, discard the old desiccant and replace with new.

3. Check that the rubber grommet is intact and in place in the base of the inner section and then re­assemble the head assembly. Otherwise replace the grommet seal if necessary, applying a trace or
silicon grease and ensuring the seal is in place correctly and the sensor will travel up and down it
without displacement or contamination with silicon grease of the sensor filters

9.3 Batteries and Battery Check

When the battery check position is selected the reading should be in the green sector, or to the

right of it. If the reading is to the left of the green sector (drier), then the batteries should be
replaced.

The instrument is supplied with 6 Varta 2014 R14 batteries. In normal use these will last for one to two

years.

This instrument is only certified Intrinsically Safe to T6 with the use of Varta 2014 batteries as supplied.

The use of other batteries invalidates the certification of the equipment for use in hazardous areas.

To replace the batteries, first remove the instrument from its carrying case. The battery holders will be

found on the instrument back panel, and protected by a metal plate. Remove the plate by removing the
2 special screws with the key provided, take off the cap of each battery carrier, and replace the
batteries with 6 c-size (R14) cells. Always replace all 6 batteries at the same time, and do not leave
completely discharged batteries in the instrument. This must be carried out in the Safe Area.

SADP_Operating_ Instructions_0114

9.4 Temperature

Typical ambient variations experienced throughout the world are quite acceptable, but avoid

placing the instrument in direct sunlight or near a source of radiant or convected heat. In countries
that experience extremes of temperature, always carry out the Automatic Calibration with the
instrument at its operating temperature.

9.5 Pressure

The Automatic Dewpoint Meter operates with the sensor at atmospheric pressure, and the
readings given in Dewpoint temperature and parts per million are therefore correct at 1 bar (A).
However, Dewpoint temperature is directly proportional to pressure, and the results obtained from
the instrument can be referred to any other pressure by use of the pressure calculator, which is
supplied with the instrument. Instructions for the use of the calculator are printed on it.

9.6 Response Time

The response time of any water vapour pressure detector will naturally be very much quicker from
dry to wet, than from wet to dry. This is the reason that the Shaw Automatic Dewpoint Meter is so
successful. The sensor is kept in a dry condition when it is not in use, and therefore results are
obtained in the quickest possible time.

To check whether a particular instrument is within specification, carry out the Automatic Calibration
procedure, close the instrument head and note the reading 10 minutes later. If the unit has not
dried down to –40°C after this 10 minute period the instrument, should be returned to your local
dealer for examination.

9.7 Guarantee

All Shaw products are guaranteed conditionally for a period of two years from purchase, exceptions

being accidental damage, or damage caused by misuse or abuse. This period may be reduced to one
year if the instrument is purchased from the stock of one of our overseas dealers. A Guarantee
certificate is available by request.

SADP_Operating_ Instructions_0114

10 BASIC DEFINITIONS

WATER VAPOUR PRESSURE: is the pressure exerted by the water vapour contained in any mixture

of gases. The total pressure exerted by the gas mixture is the sum of the pressures exerted by its
components — including the water vapour. Water Vapour Pressure varies in direct proportion to the
total gas pressure.

DEWPOINT TEMPERATURE: is defined as the temperature to which the gas must be cooled in order

that it should be saturated with water vapour (i.e.: 100% relative humidity.) For practical reasons it is
referred to water above 0 deg C and ice below 0 deq C.

PARTS PER MILLION BY VOLUME: PPM(v) or VPM is the ratio of the water vapour pressure to the

total gas pressure.

PARTS PER MILLION BY WEIGHT: PPM(w) is the same as VPM, except that the figure is modified

according to the ratio of the molecular weight of water vapour to the molecular weight of the carrier gas
mixture.

RELATIVE HUMIDITY: is the ratio of the actual water vapour pressure in the gas to the saturation water

vapour pressure at the same temperature.

SADP_Operating_ Instructions_0114

11 Electrical Function Check

If there is any doubt about the functioning of the Analyser, the following test may be carried out.
(This must always be carried out in the Safe Area)

1. Switch the instrument off.

2. Check that the meter reading is accurately at the zero (left-hand) end of the scale.
If not, adjust the reading by means of the plastic screw on the meter face.

3. Remove the instrument head by taking out the 3 screws in the base flange, and disconnect the
sensor by pulling out the coaxial plug.

4. Switch instrument to the Battery Check position to confirm that the batteries are in good condition
(replace them if they are not), and then select the read position

(the standard range on extended range models).

5. Apply a short circuit to the sensor cable plug on the instrument - the voltage is extremely low and
so there is no hazard.

6. Adjust the Automatic Calibration control to give a reading of full scale. (i.e. on the Automatic
Calibration line).

7. Remove the short circuit and the reading should return to the left-hand end of the scale. This
establishes that there is no major fault in the instrument. If the tests so far do not produce the
expected results, the instrument should be returned to your local dealer.

8. Apply a load of 8.6k Ω to the sensor cable plug. Readjust the reading to full scale, using the
Automatic Calibration Control.

9. Increase the load to 18.6k Ω. The reading should decrease to 62% of scale ±1%.

10. Increase the load to 62k Ω. The reading should decrease to 23.5% of scale with the same
tolerance as above.

11. Refit the head assembly, and carry out the Automatic Calibration procedure.

This Completes The Electrical Function Check

N.B. Please note that VP1 on the printed circuit board is factory set. If the adjustment of this

control is altered, it will be necessary to return the instrument to our works.

SADP_Operating_ Instructions_0114

12 Problem Guide

PROBLEM CAUSE SOLUTION

ERRATIC READINGS Static on Indicator Moisten indicator face with 50/50 mixture of
detergent & water, or use proprietary anti-static
cleaner. DO NOT POLISH INDICATOR FACE.

FULL SCALE READING Wet gas Stop gas supply & switch analyser off.

Short Circuit Sensor Disconnect plug from sensor & if the indicator
Cable or Plug still reads over full scale deflection. Cure the
short circuit in the cable or plug or replace.

Short Circuit Sensor Disconnect the plug from the sensor & note the
indicator falls to 0 deflection. Apply approx 24V
DC to sensor terminals MOMENTARILY with
the sensor in a dry condition. Polarity is not
important, but the contact must be brief or the
sensor may be damaged. If this fails to clear the
fault the sensor must be replaced.

ZERO READING Open Circuit on Cable Disconnect plug from sensor and connect centre
pin of plug to the outer connection. No reading
will be obtained. Repair cable.

Open Circuit on Sensor Test as for open circuit on cable, but note that
reading over FSD obtained. Check sensor
connection or replace sensor.

Autocal Wrongly Set. Readjust to correct setting (i.e. carry out the
Autocal procedure as on page 4).

Instrument Disconnect coaxial cable from instrument and
Unserviceable connect short circuit across terminals and note
no reading even with Autocal control turned up.
Return instrument for service.

WET READING Leak in System or Cure leak, or replace unsuitable pipe with
use of Unsuitable Pipe copper or stainless steel. Flexible connections

should be made with PTFE pipe. NEVER use
rubber or plastic pipe.

Comparison with Ensure that samples are taken from same sample
Secondary Standard point. Re-check Autocal setting. If problems still
Instrument or occurs change sensor.
Calibration Gas

SADP_Operating_ Instructions_0114

SLOW RESPONSE Free Water in System Check drain & inspection ports in the main system
& sample pipe work.

Wrongly Sized or Refer to Section 3.2 of manual. & ensure sample
Incorrect Material on tube material & flow rates are as
Sample Lines recommended.

DRY READING Autocal Wrongly Set Refer to Section 7.0 of manual & re-check Autocal.
If this does not cure problem return for
calibration.

Comparison with Refer to Section 7.0 of manual & re-check Autocal.
Secondary Standard If this does not cure problem return for calibration.
Instrument or Calibration
Gas

CONSTANT READING Condensation in Sample Condensation will occur if temperature of the

System sample system, or main pipe, at any point is below
(colder) than the DP temperature of the sample
gas. Once having formed, the sample reaching the
sensor will have a DP equal to temperature of
the condensate, regardless of the DP at the sample
point.

SADP_Operating_ Instructions_0114

13 Hygrometric Equivalents

SADP_Operating_ Instructions_0114

SADP & SADP-D Specification

Accuracy:

+/-1PPM , (+/-3 deg.C DP Red Spot, +/-4 deg.C DP, all others).

Type:

Portable hygrometer in stove enamelled zinc plated steel and alloy
case, complete with padded carrying case. For table top or portable
use with desiccant chamber for rapid readings. Certified intrinsically
safe for operation in hazardous areas.

ATEX: Intrinsically Safe to Ex II I G Ex ia IIC T6 Ga
FM: Intrinsically Safe Class 1, Division 1, Groups A&B, C, D, T6.

Dimensions / Weight:

Overall dimensions: 202mm x 225mm x 276mm High (320mm with
head extended) Weight: 4 Kg approx.

Display:

SADP 12cm Taut Band indicating meter showing Dewpoint and
ppm, with amplified range of 0-10ppm on TR versions.
SADP-D 2cm 3 1/2 Digit LCD with battery check symbol.

Sensor Connection:

Internal.

Power Supply:

9V DC ( 6 x VARTA 2014 R14 cells ) Internal

Sampling:

Pressure: atmospheric with flow rate of 5 - 10 litres/minute

Outputs:

None.

Calibration:

Autocal on all but Blue range.

Accessories / Options:

SU4 Lo, Med or Hi Sample system for sample conditioning
pressurised gases to atmospheric conditions and controlled flow.

Sensor Type {r}:
Purple: {P}
Red: {R}

Sensor Range:

-100 / 0 deg.C DP, 0-6000ppm, (auto-cal)

-80 / -20 deg.C DP, 0-1000ppm, and 0-10 on TR version, (auto-cal)

Grey : {G} -80 / 0 deg.C DP, 0 - 6000 ppm, and 0-10 on TR version, (auto-cal)
Blue : {Bl} -80 / +20 deg.C DP, 0 - 23,000 ppm (manual-cal)

To Order:

Analogue versions SADP {r}: suffix TR if required for G and R
ranges only.
Digital Versions SADP-D-{r}

SADP_Operating_ Instructions_0114