INSTALLATION AND OPERATING INSTRUCTIONS

Transcription

1 Labkotec Oy Labkotie 1 FI KANGASALA FINLAND Tel Fax Internet: / 5 Capacitive level sensor KAS/3W INSTALLATION AND OPERATING INSTRUCTIONS The KAS/3W wire probe is intended for level measurement for dry powdery materials in metal tank. The measurement is based on the variation of the probe's capacitance as a function of level where the metal tank acts as a counter electrode of the capacitor. Typical applications are cement, lime, sand and other powdery materials. When ordering please specify probe length L and medium to be measured. Application example

2 2 / 5 1. TECHNICAL DATA TRANSMITTER TYPES SUPPLY VOLTAGE OUTPUT CURRENT MEASURING RANGE The characteristics of the measurement control unit may affect the range. MEASUREMENT ERROR Of max. measuring range MAX. MEASURING CAPACITANCE TEMPERATURE DRIFT Of max. measuring range MET3 / VL / V / R Vdc approx. 6 ma at max. measuring capacitance (load 300 S) VL approx :A/pF V approx. 10 :A/pF R approx. 1,2 :A/pF Cement, lime [VL] ,6 m [V] 0-3, m Dry sand [VL] 0-0,5... 1,8 m [V] m [R] m ±1% VL V R 150 pf 650 pf 5500 pf 2. SENSOR ASSEMBLY The sensor consists of a transmitter and a wire type sensing element with a weight. The sensor is supplied from the manufacturer as a complete assembly. 3. PROBE LENGTH The probe's length L (Fig. 1) refers to the distance from the bottom of the probe weight to the sealing surface of the transmitter. The actual measuring range begins from the top of the weight. Fig. 1 ± /C 0/C < >+50/C MATERIALS Wetted parts Transmitter housing AMBIENT TEMPERATU- RE Sensing element Transmitter ±1% ±2% Zinc coated steel, PVC Cast aluminium /C /C CONNECTION R1 ½" CABLE min. (3 +1) x 0,5 mm 2 EMC Emission Immunity Shielded pair instrument cable e g 2 x (2+1) x 0,5 mm 2. When buried in the ground, armoured cable must be used. EN EN EN NOTE! The measurement is based on changes in the probe's capacitance - variations in the dielectic constant or electrical conductivity of the medium to be measured will affect measurement results. KAS/3W probes can be used, for example, with the POP-22 measurement control units manufactured by Labkotec Oy. The probe length L is determined on the basis of the target environment; the probe wire with its weight must fit in the tank.

3 3 / 5 Fig. 2

4 4 / 5 4. ELECTRICAL CONNECTIONS Fig. 3 After setting up the probe, the cable between probe and control unit is connected to the terminals marked SIG- NAL LINE on the probe according to Fig. 2. Take into account the connection and installation instructions for the control unit as well. Fig. 2a shows all shields connected to the earthing screw inside the probe housing. In this case the shields are not connected at the other end to equipotential ground. NOTE! If a cable shield is connected to equipotential ground at the other end (Fig. 2b) it is not connected to probe earthing. In this case the cable shield must also be isolated from probe frame and from other shields. For connections with a cable having only single shielding: The shield is connected either to the earthing screw inside the housing or to equipotential ground as shown in Fig. 2c, taking into account the instructions given above. NOTE! Use of one shield alone may weaken the system's immunity to interference. The earthing screw outside the housing is connected to equipotential ground using a yellow-green conductor of at least 2 x 1.5 mm 2 or 1 x 4 mm 2. The conductor's resistance may not exceed 1 S. Ensure that the metal tank and the transmitter housing are galvanically connected with each other. Fig. 3 shows the transmitter housing without lid and equipped with the electrostatic discharger "A" available as an accessory. If it is to be expected that large static charges appear in the target environment an electrostatic discharger ESD10 ("A", Fig. 3) can be connected between the transmitter module and the probe element. The colours for the conductors of the discharger are marked as follows: B for a red, C for a blue and D for a green conductor. 5. POINTS TO NOTE

5 5 / 5 If the probe gives erroneous values, check the following: The width of the housing is 92 mm. 1. Has the cable been connected correctly? 2. Is there too thick buildup of the medium on the measuring electrode? 3. Has the insulation of the measuring electrode been damaged? 4. The wire must not touch the tank frame. 6. ORDERING INSTRUCTIONS Specify: - medium to be measured? - probe length L? The correct type of transmitter to suit the probe is selected at factory on the basis of medium and probe length. The type is marked clearly on the name plate inside the transmitter housing. 7. OTHER PROBES IN THE LABKOTEC 3W SERIES PA/3W - tubular probe PAH/3W - tubular probe form acid-proof steel SA/FEP/3W - rod probe for viscous and aggressive liquids KAH/3W - cable probe for water KAR/SA/3W - cable probe for aggressive liquids, pressure max 25 bar VEH - counter electrode for the KAH probe THERMAL BARRIER TUBE for applications where tank surface temperature exceeds +60 C 8. PROBE DIMENSIONS