BEKA BA538C Manual

Contents

53.3 Pulse inputAs shown in Fig 2, the BA538C will count pulsesfrom a wide variety of transducers enabling it todisplay the output from almost any flowmeter.The instrument has one pulse input, but two setsof input terminals enable it to accommodatedifferent types of transducers. Terminals 3 and 4are for voltage pulse inputs and terminals 5 and 6are for pulse sources that need powering i.e.proximity detectors, switches and open collectors.Note: Only one pair of input terminals may beused at a time. i.e pulses can not be countedfrom terminals 3 & 4 and from terminals 5 & 6 atthe same time.The following table shows the switchingthresholds for the various transducers, plus themaximum operating frequency and the inputterminal numbers. For reliable counting the inputsignal must fall below the lower threshold and riseabove the upper threshold.SwitchingthresholdsFreqmaxInputterminalsSwitch 100 1000 100Hz 5 & 6Proximitydetector1.2mA 2.1mA 5 kHz 5 & 6Opencollector2k 10k 5kHz 5 & 6Magneticpick-off0mV 20mVpeak5kHz 3 & 4Voltagepulse1.0V 3.0V 5kHz 3 & 43.4 Remote resetThe BA538C total display is reset to zero whenterminals 7 & 8 are connected together for morethan one second. Permanent interconnection ofthese terminals will stop totalisation and may beused as an inhibit function. There is no practicallimit on the distance that the reset switch may befrom the totaliser.Alternatively, the BA538C may be programmed sothat the total display is reset to zero when the Upand Down push-buttons are operatedsimultaneously for more than two seconds. – see5.124. INSTALLATION4.1 LocationThe BA538C is housed in a robust aluminiumenclosure with a polyester membrane front panelsurrounded by a Noryl bezel. The front of theinstrument provides IP65 protection and a gasketseals the joint between the instrument enclosureand the panel. The instrument may be installed inany panel providing the environmental limitsshown in the specification are not exceeded.Although the front panel of the instrument hasIP65 protection, the BA538C is not intended forexternal mounting. Please refer to BEKAassociates if external mounting is required.Fig 3 shows the overall dimensions of the BA538Cand the panel cut-out. To achieve an IP65 sealbetween the instrument enclosure and the panelthe smaller cut-out must be used and theinstrument secured with four panel mounting clips.The BA538C liquid crystal display has maximumcontrast when viewed from directly ahead andslightly below the centre line of the instrument.For reflective displays there is little degradation ofcontrast when viewed from above the centre line,but slight degradation may be noticeable when theinstrument is fitted with a backlight.Fig 3 BA538C dimensions