G4 Multi Channel Weighing Instrument. PM/DT/HE Technical Manual

Technical ManualFunctionsMeasurement with strain gauge transducers.Both excitation voltage and output signal are measured at the transducer to avoidinfluence from voltage drop in the connection cable. Excitation to the transducer, fromthe G4 Instrument is provided over separate wires.A shielded 6-wire cable must be used to connect a distant transducer to the instrument.A/D conversion.The analog signals from the transducer are converted to digital form and filteredto give an internal transducer signal with high resolution.Calculation.The transducer excitation and signal values are combined to form an internaltransducer signal, representing the load on the transducer. Influenced by calibrationdata, this signal is converted to a digital measurement value, the weight value, whichcan be presented at the local display window and at external equipment.Error supervision.As long as the error supervision detects no error, the signal ‘In process’ is presentbut if an error is detected, ‘In process’ will be off and a specific error message will bedisplayed. ‘In process’ can be set to control any digital output. Note that there areweighing channel specific and instrument specific error detection.Levels.32 level comparators in the instrument can be set to switch at defined signal levels withany selected hystereses added, meaning that the switch level can be different forincreasing and decreasing signal. Output signals from these comparators are availableon the serial communication. The level comparator outputs can also be set to controldigital outputs from the instrument.Communication.The G4 Instrument utilizes the serial interface, Ethernet and a fieldbus interface forcommunication with control computer. The serial interface consists of a RS-232(COM1) connection and a RS-485/RS-422 (COM2) connection. COM2 can be usedwith 2- or 4-wire connection.Weight values, level status, error status etc. can be collected and commands giventhrough the communication interfaces. Modbus RTU protocol is used for the serialinterfaces and Modbus TCP for the Ethernet connection. For the optional fieldbusinterface Profibus or DeviceNet can be used.Instrument modes.In normal operation mode the G4 Instrument is presenting the measurement values onthe front panel graphical display. One or more weighing channels can be shownsimultaneously. The user can configure the display via set-up parameters.During parameter set-up the instrument will continue normal operation. However ifhardware set-up parameters have been changed the instrument will be restarted.The operator will always be notified before the instrument is restarted.Parameter setting.In the instrument all operating functions are controlled by set-up parameters withnumerical values, string values, or pre-selected values from a list of alternatives.Parameter set-up is performed by the keys at the front panel of the instrument and/orby using the buttons displayed on the touch display.1-2