wtw MultiLine FDO 925 User manual

OPERATING MANUAL
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FDO®925
FDO®925-P
OPTICAL D.O. SENSOR
FDO®925
FDO®925-P

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FDO®925
Copyright © 2015, WTW GmbH
Reproduction in whole - or even in part - is prohibited without the
express written permission of WTW GmbH, Weilheim.
Printed in Germany.
For the most recent version of the manual, please visit
<hyperlink>www.si-analytics.com.

FDO®925 Contents
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FDO®925 - Contents
1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Recommended fields of application . . . . . . . . . . . . . . . . . 5
2 Measuring / Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 General information on the handling of the sensor cap . . 6
2.2 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Opening and closing the IDS plug connection (FDO®925-P)
7
2.4 Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Function check and user calibration . . . . . . . . . . . . . . . . . 8
2.6 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Maintenance, cleaning, replacement . . . . . . . . . . . . . . . . 10
3.1 General maintenance instructions . . . . . . . . . . . . . . . . . . 10
3.2 Exchanging the sensor cap . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Cleaning the sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4 Checking the zero point of the sensor . . . . . . . . . . . . . . . 13
4 What to do if... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6 Wear parts and accessories . . . . . . . . . . . . . . . . . . . . . . . 18

Overview FDO®925
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1Overview
1.1 Structure and function
Structure
1Shaft
2Connecting head with active sensor electronics
3Connection cable (FDO®925)
4IDS plug (FDO®925-P)
5Protective hood, with connection for RZ 300 stirrer (accessory)
6Sensor membrane
7SC-FDO®925 sensor cap with memory chip
8Gold-plated contacts for the memory chip of the sensor cap
9Locking device
10 Measurement window
11 O-ring
12 Thermistor enclosure with temperature sensor
12
3
4
7
9
512811106
FDO 925
®
FDO 925-P
®

FDO®925 Overview
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Sensor cap with
memory chip
A memory chip is integrated in the sensor cap. The following data are stored
on the memory chip:
Type designation of the sensor cap
Series number
Data of the factory calibration or user calibration
Intelligent
membrane (IQMC
technology)
For each membrane, the individual calibration values are determined by
a factory calibration process and stored to the memory chip of the sensor
cap, ensuring maximum accuracy over the whole lifetime of the
sensor.
Automatic sensor
recognition
The data of the sensor and sensor cap is recalled by the meter when the
sensor is connected and is used for measurement and for measured value
documentation. The calibration data are stored in the sensor cap. Thus, the
calibration is automatically retained if the sensor or meter are exchanged.
The digital transmission technique guarantees the failure-free communica-
tion with the meter even with long connection cables.
Firmware update You can update the firmware of the IDS sensor using your meter.
Details on the firmware update are given in the current operating manual of
your meter.
The current operating manual of your meter and the firmware update for the
sensor are available on the Internet under www.WTW.com.
1.2 Recommended fields of application
Recommended
fields of
application
On site measurements in rivers, lakes and wastewater
Applications in water laboratories
BOD measurements

Measuring / Operation FDO®925
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2 Measuring / Operation
2.1 General information on the handling of the sensor cap
Despite its exterior robustness, the sensor is a high precision optical instru-
ment. Therefore, you should take the following precautions when dealing with
the FDO®925:
Please do not touch the sensor membrane with your fingers
Avoid any great mechanical stress of the sensor membrane (pressure,
scratches).
2.2 Commissioning
Scope of delivery D.O. sensor FDO®925 with sensor cap
Check and storage vessel, FDO®Check
Operating manual
Preparing the
sensor for
measurement
FDO®925 Connect the sensor to the meter.
The sensor is immediately ready to measure.
FDO®925-P Connect the sensor to a free IDS sensor plug-in
position of the multi parameter probe or to an IDS
connection of the meter. To open and close the
IDS plug-in position please note the
section 2.3 OPENING AND CLOSING THE IDS PLUG
CONNECTION (FDO®925-P).
The sensor is immediately ready to measure.
Connection cables in different lengths to connect
the FDO®925-P sensor to the meter are listed in
chapter 6 WEAR PARTS AND ACCESSORIES.

FDO®925 Measuring / Operation
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2.3 Opening and closing the IDS plug connection (FDO®925-P)
Opening the plug
connection
If necessary, clean the plug connection
Open the locking device (step 1)
Use your thumb and index finger to press the clips of the connector
together, and pull the connector out of the plug (step 2).
Closing the plug
connection
Make sure that the plug connection is completely dry and clean.
Align the guidance of the connector with the groove in the plug and insert
the connector in the unlocked plug until it catches (step 3).
Close the locking device (step 4).
This section only applies to the IDS plug variant,
FDO®925-P.
2
4
3
1
Plug connection
closed and locked
Guidance
Groove

Measuring / Operation FDO®925
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2.4 Measuring
Minimum depth of
immersion
Observe the required minimum immersion depth (see chapter 5 TECHNICAL
DATA).
Incident flow The FDO®925 D.O. sensor enables precise measurements without any inci-
dent flow.
However, an incident flow of the sensor membrane improves the responding
behavior of the sensor (see chapter 5 TECHNICAL DATA). The incident flow can
be provided in different ways, e. g.:
The flow of the water to be measured is sufficient (aeration tank, water
pipe, stream)
Slowly pull the sensor through the water by hand (lake, container), or
Use a flow aid such as a magnetic stirrer with stirring device (see
chapter 6 WEAR PARTS AND ACCESSORIES)
2.5 Function check and user calibration
Factory calibration The FDO®925 is factory calibrated. In the recommended application (see
page 5), the measuring characteristics of the sensor cap remain stable for the
specified service life. Thus, a user calibration is not usually required.
When does a
check or user
calibration make
sense?
A function check or user calibration can be useful in the following special
cases:
If the measured values appear to be implausible and it is assumed that the
service life of the sensor cap is over
Routinely within the framework of the company quality assurance.
Check- or
calibration
medium
The check and user calibration take place in water vapor-saturated air. The
suitable conditions are easily provided with the aid of the check and calibra-
tion vessel, FDO®Check. For this purpose, moisten the sponge inside the
vessel. Then insert the sensor in the vessel as far as it will go. The sensor
membrane must be clean and dry for this.
Moisten the sponge:
Remove the cap (1).
Take out the sponge (2), wet it, then slightly squeeze it out.
Insert the sponge again and close the calibration and storage vessel with
12

FDO®925 Measuring / Operation
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the lid.
After inserting the sensor, wait for the temperatures of the sensor and cali-
bration vessel to adjust.
2.6 Storage
Always store the sensor in the check and storage vessel (FDO®Check) at a
temperature in the range 0 ... 50 °C (32 ... 122 °F).
The steps of the check or user calibration are described in detail
in the operating manual of the meter.

Maintenance, cleaning, replacement FDO®925
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3 Maintenance, cleaning, replacement
3.1 General maintenance instructions
Handling of the
sensor cap
Despite its exterior robustness, the sensor is a high precision optical instru-
ment. Therefore, special care should be taken when doing any maintenance
or cleaning work:
Dirt and moisture under the sensor cap can affect the functioning and
shorten the service life of the sensor cap. Therefore, make sure the work-
ing environment is clean and dry prior to removing the sensor cap.
Please do not touch the outer sensor membrane with your fingers. Touch
the sensor cap at the sides only (arrows in figure on the left).
Avoid any great mechanical stress of the sensor membrane (pressure,
scratches).
Exposure to light, particularly daylight, of the interior of the sensor cap will,
by-and-by, affect the measurement characteristics and shorten the ser-
vice life of the sensor cap. Therefore, the interior of the sensor cap should
not be exposed to direct sunlight. Avoid any exposure to light that exceeds
the extent required for necessary maintenance and cleaning activities.
Store dismantled sensor caps in a light-protected environment only.

FDO®925 Maintenance, cleaning, replacement
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3.2 Exchanging the sensor cap
To exchange the sensor cap, proceed as follows:
Removing the
sensor cap
Mounting the
sensor cap
Before removing the sensor cap, observe the general mainte-
nance instructions in section 3.1.
1. Pull the sensor out of the sample.
2. Clean the outside of the sensor (see section 3.3.1).
3. Unscrew the protective hood from the sensor by hand.
4. Thoroughly clean and dry the sensor head once again.
5. Grasp the sensor cap on the sides (arrows in figure on the left) and
remove it by pulling it away from the sensor in a straight upward
direction.
Caution:
Do not push any tools or other sharp objects between the sealing sur-
faces. This would damage the sealing surfaces and sealing ring.
6. Check the front surface of the sensor for absolute cleanness and
clean it if necessary (see section 3.3.2).
7. Thoroughly clean the thread of the protective hood.
8. Check the sealing ring for intactness and correct position.
The sealing ring has to be replaced if it is damaged.
9. Aim the sensor head upwards and place the new sensor cap on the
sensor. The locking device on the sensor head must be inserted into
the receptacle on the inside of the sensor cap (see figure on the left).
10. Put the protective hood on the sensor head and screw it tight by hand
as far as it will go. A gap of approx. 0.8 mm remains between the pro-
tective hood and sensor.
The sensor is immediately ready to measure.
Sealing
ring

Maintenance, cleaning, replacement FDO®925
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3.3 Cleaning the sensor
3.3.1 Exterior cleaning
Dirt on the sensor can affect the measuring characteristics. Biological depos-
its for example, consume oxygen and can, when occurring on the sensor
membrane, impair the responding behavior and cause values that are too
low. Therefore, we recommend regular visual inspections and exterior clean-
ing as necessary.
Pay attention to the following points for cleaning:
First, thoroughly rinse the sensor with tapwater to remove loosely adher-
ing dirt.
Rough dirt on the sensor shaft can be brushed off with a soft brush. Atten-
tion: Do not use the brush in the area of the sensor membrane. Risk of
damage!
The sensor cap including the sensor membrane should be wiped with a
soft and moist microfiber cloth.
In the case of persisting dirt you can add some household washing-up liq-
uid to the tapwater. Attention: Never use any alcohol for cleaning!
3.3.2 Interior cleaning of sensor cap and sensor head
If moisture or dirt have penetrated under the sensor cap, e.g. because the
sensor cap is damaged, you can make the sensor ready for operation again
as follows:
NOTE
Only use nonabrasive, alcohol-free detergents, as otherwise the optical
surfaces could be damaged.
1. Remove the sensor cap (see section 3.2).
2. Clean the sensor head and sensor cap:
– Rinse all inner surfaces with tapwater
– Remove contamination containing fat and oil with warm water and
household washing-up liquid
– Then rinse all inner surfaces with deionized water
3. Pat dry all surfaces with a clean, lint free cloth.
4. Allow the sensor and sensor cap to dry completely at a dry location
so moisture can evaporate even from corners difficult to access.
When doing, so protect the inside of the sensor cap from light.
5. Put the sensor cap on (see section 3.2).

FDO®925 Maintenance, cleaning, replacement
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3.4 Checking the zero point of the sensor
There are two methods to check the zero point of the sensor:
Measurement in a nitrogen atmosphere (recommended method)
Measurement in a sodium sulfite solution according to DIN EN 25814/
ISO 5814.
Test criterion The sensor is OK if the measuring instrument displays < 0.5 % D.O. satura-
tion after 15 minutes.
If the sensor cap is visibly damaged it has to be replaced.

What to do if... FDO®925
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4 What to do if...
Error symptom Cause Remedy
No temperature value
or D.O. value
– No connection between meter
and D.O. sensor
– Establish connection between
meter and D.O. sensor
– Cable defective – Return the D.O. sensor
Measured value too
high or too low
or
error message,
Error
– Coating on sensor cap – Clean the outside of the sensor
(see section 3.3.1)
– Membrane damaged – Exchange the sensor cap
– Service life of the sensor cap
over
– Check the sensor
– Replace the sensor cap as nec-
essary (see section 3.2)
– Dirt inside the sensor cap and
sensor head.
– Protective hood not properly
tightened.
– Sensor cap untight or defective.
– Dismantle the sensor cap
– Clean the insides of the sensor
cap and sensor head (see
section 3.3.2)
– Mount the sensor cap correctly
and tighten the protective hood
as far as it will go (see
section 3.2)
– Replace a defective sensor cap
as necessary
Incorrect temperature
display
– The temperature sensor is not
immersed deep enough in the
measuring solution
– Observe the minimum immer-
sion depth
– Temperature sensor defective – Return the D.O. sensor
Error message,
no cap
– No sensor cap put on – Clean the sensor head and sen-
sor cap
– Sensor cap not recognized – Return the D.O. sensor
– Sensor cap defective – Replace the sensor cap

FDO®925 Technical data
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5 Technical data
General features Measuring principle Optical measurement based on photolumi-
nescence.
Temperature sensor Integrated NTC 30 (30 kat 25 °C / 77 °F)
Dimensions
(in mm)
Weights FDO®925 180 g (with 3 m cable)
FDO®925-P 107 g
FDO®Check 58 g
Materials Shaft POM
Connection head POM
Sensor cap PVC, silicone and PMMA
Sensor head POM, PV and PMMA
Sensor head - sensor cap
contacts
Brass, gold-plated
Thermistor housing VA steel 1.4571
Protective hood VA steel 1.4571
Seals FPM (Viton)
150.0
150.0
205.5
252.1
15.3
15.3
21.7
21.7
FDO 925:
®
FDO 925-P:
®

Technical data FDO®925
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Connection cable
(FDO®925)
Lengths 1.5 or 3 m
Diameter 4.3 mm
Smallest allowed
bend radius
Fixed installation: 20 mm
Flexible use: 60 mm
Plug type Socket, 4 pins
IDS plug
(FDO®925-P)
Connection type 4-pole, watertight plug connection with lock,
reverse polarity protected
Materials Synthetic materials: Glass fiber reinforced
Noryl, TPU, TPC-ET, POM, PEEK, PBT
O-ring: FPM
Contacts gold-plated
Pressure
resistance
Sensor with connection
cable
IP 68 (1 x 106Pa or 10 bar)
Cable plug (FDO®925) IP 67 (when plugged in)
The FDO®925 meets the requirements according to article 3(3) of the 97/
23/EC directive ("Pressure equipment directive").
Measurement
conditions
Measuring ranges at 20 °C
(68 °F)
0 ... 20 mg/l D.O.
0 ... 200 % D.O.saturation
0 ... 400 mbar D.O. partial pressure
Temperature range 0 ... 50 °C (32 ... 122 °F)
Max. admissible overpres-
sure
1 x 106Pa (10 bar)
Immersion depth min. 6 cm
max. 100 m (depending on the cable length)
Operating position any
Approach flow not required
Storage conditions Recommended storing
method
in the check and storage vessel, FDO
®Check
Storage temperature 0 ... 50 °C (32 ... 122 °F)

FDO®925 Technical data
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Characteristic data
on delivery
Accuracy of D.O. measure-
ment at 20 °C (68 °F) in air-
saturated water
± 1.5 %
Zero signal ≤0.02 mg/l O2
≤0.2 % O2 saturation
≤0.4 mbar O2 partial pressure
Response time at 20 °C
(68 °F) in stirred solution
t90 (90 % of the final value display after)
< 30 s
t95 (95 % of the final value display after)
< 45 s
t99 (99 % of the final value display after)
<60s
Response time of tempera-
ture measurement
t99 (99 % of the final value display after)
<60s
Precision of temperature
measurement
± 0.2 K
Working life of the sensor
cap
Min. 1 year with authorized use

Wear parts and accessories FDO®925
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6 Wear parts and accessories
Wear parts and
maintenance
equipment
Description Model Order no.
Replacement sensor cap SC-FDO®925 201 310
Replacement protective hood ADA FDO®/RZ 201 312
General
accessories
Description Model Order no.
Calibration and storage vessel FDO®Check 201 311
Magnetic stirrer Oxi-Stirrer 300 203 810
Stirring accessory - provides a constant,
defined flow to the sensor, in conjunction
with the Oxi-Stirrer 300. The stirring acces-
sory is put on the protective hood.
RZ 300 203 824
Funnel set - for BOD measurements in Win-
kler bottles
TS 19 205 710
Karlsruhe bottle - suitable for BOD measure-
ment
KF 12 205 700
Fixing ring, recommended for measure-
ments in Karlsruhe bottles
FR 19 205 712
Flow-through accessory - for pressure-free
D.O. measurement with flow-through quanti-
ties from 25 to 65 ml/min.
D 201 203 730
Accessories for
FDO®925-P (IDS
plug variant)
Description Model Order no.
IDS connection cable, 1.5 m AS/IDS-1.5 903 850
IDS connection cable, 3 m AS/IDS-3 903 851
IDS connection cable, 6 m AS/IDS-6 903 852
IDS connection cable, 10 m AS/IDS-10 903 853
IDS connection cable, 15 m AS/IDS-15 903 854
IDS connection cable, 20 m AS/IDS-20 903 855
IDS connection cable, 25 m AS/IDS-25 903 856
IDS connection cable, 40 m AS/IDS-40 903 857
IDS connection cable, 60 m AS/IDS-60 903 858
IDS connection cable, 100 m AS/IDS-100 903 859
Blind plug for IDS plug BPO/IDS 900 908 371
Further accessories are listed in the price list of the WTW catalog
"Laboratory and field instrumentation".

Wissenschaftlich-Technische
Werkstätten GmbH
Dr.-Karl-Slevogt-Straße 1
D-82362 Weilheim
Germany
[phone]
[phone]
[e-mail]
www.wtw.com
Tel:
Fax:
E-Mail:
Internet:
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