Operating manual FDO® 925 Optical D.O.
FDO® 925 Note The latest version of the present operating manual can be found on the Internet under www.WTW.com. Copyright 18 © Weilheim 2010, WTW GmbH Reprinting - even as excerpts - is only allowed with the explicit written authorization of WTW GmbH, Weilheim. Printed in Germany.
FDO® 925 Contents Contents 1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.1 Structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.2 Recommended fields of application . . . . . . . . . . . . . . . . 22 2 Measuring / Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1 2.2 2.3 2.4 2.5 3 04/2010 23 23 23 24 24 Maintenance, cleaning, replacement . . . . . . . . . . . . . . . . 25 3.1 3.2 3.3 3.
FDO® 925 Contents 20 ba75898S01 04/2010
FDO® 925 Overview 1 Overview 1.1 Structure and function 1 Structure 2 7 3 Sensor cap with memory chip 4 5 6 8 9 10 1 Shaft 2 Connection head 3 Fixing ring 4 Sensor membrane 5 SC-FDO® 925 sensor cap with memory chip 6 Gold-plated contacts for the memory chip of the sensor cap 7 Locking device 8 Measurement window 9 O-ring 10 Thermistor enclosure with temperature sensor A memory chip is integrated in the sensor cap.
FDO® 925 Overview 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 communication with the meter even with long connection cables.
FDO® 925 Measuring / Operation 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 instrument. Therefore, you should take the following precautions when dealing with the FDO® 925: z Please do not touch the sensor membrane with your fingers z Avoid any great mechanical stress of the sensor membrane (pressure, scratches). 2.2 Scope of delivery Commissioning z D.O.
FDO® 925 Measuring / Operation 2.4 Function check and user calibration Factory calibration The FDO® 925 is factory calibrated. In the recommended application (see page 22), the measuring characteristics of the sensor cap remain stable for the specified service life. Thus, a user calibration is not usually required.
FDO® 925 Maintenance, cleaning, replacement Handling of the sensor cap 3 Maintenance, cleaning, replacement 3.1 General maintenance instructions Despite its exterior robustness, the sensor is an optical high precision instrument. Therefore, special care should be taken when doing any maintenance or cleaning work: z Dirt and moisture under the sensor cap can affect the functioning and shorten the service life of the sensor cap.
FDO® 925 Maintenance, cleaning, replacement 3.2 Exchanging the sensor cap Note Before removing the sensor cap, observe the general maintenance instructions in section 3.1. To exchange the sensor cap, proceed as follows: Removing the sensor cap 1 Pull the sensor out of the sample. 2 Clean the outside of the sensor (see section 3.3.1). 3 Unscrew the fixing ring from the sensor by hand. 4 Thoroughly clean and dry the sensor head once again.
FDO® 925 Maintenance, cleaning, replacement 3.3 Cleaning the sensor 3.3.1 Exterior cleaning Dirt on the sensor can affect the measuring characteristics. Biological deposits 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 cleaning as necessary.
FDO® 925 Maintenance, cleaning, replacement Note If the sensor cap is visibly damaged it has to be replaced. 3.4 Checking the zero point of the sensor There are two methods to check the zero point of the sensor: z Measurement in a nitrogen atmosphere (recommended method) z Measurement in a sodium sulfite solution according to DIN EN 25814/ ISO 5814. Test criterion 28 The sensor is OK if the measuring instrument displays < 0.5 % D.O. saturation after 15 minutes.
FDO® 925 What to do if... 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 – 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 necessary (see section 3.
FDO® 925 Technical data 5 General features Technical data Measuring principle Optical measurement based on photoluminescence. Temperature sensor Integrated NTC 30 (30 k: at 25 °C / 77 °F) 201.5 Dimensions (in mm) 145.0 15.3 Weight Materials Connection cable Pressure resistance 21.7 180 g (with 3 m cable) 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.
FDO® 925 Technical data Measurement conditions Storage conditions Characteristic data on delivery ba75898s01 04/2010 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 overpressure 2.5 x 105 Pa (2.5 bar) Immersion depth min. 6 cm max.
FDO® 925 Wear parts and accessories 6 Wear parts and accessories Wear parts and maintenance equipment Description Model Order no. Replacement sensor cap SC-FDO 925 201 310 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. For installation on the sensor, the ADA FDO/RZ adapter is required.
