The RS-485 port is connected to the UART port on the Raspberry Pi using a SN65HVD72 interface. Although many applications use RS-485 signal levels, the speed, format, and protocol of the data transmission are not specified by RS-485. The Novus FieldLogger functioned as a versatile yet powerful data acquisition and SCADA system which the product engineer found simple to use. The product engineer then connected the FieldLogger to a Celesco SM2 miniature string pot to detect and measure linear position and velocity over time. The string pot was mounted to a fixed surface and its cable attached to the floor panel under monitoring. GSI Grain Storage installed a Novus FieldLogger data acquisition system in a grain storage bin that was repeatedly loaded and unloaded into the storage floor area to measure the separation of the floor sections. GSI Grain Storage benefitted in several key ways following installation of the Novus FieldLogger. A precision plastic hybrid 10K-ohm potentiometer delivered a voltage divider output signal that was linearly proportional to the travel of the spring-loaded measuring cable, based on the movement of the grain bins, which the FieldLogger then read and recorded at 1 reading an hour.

With an RS485 interface, the FieldLogger could act as a Modbus RTU master and read registers from other slaves, and as a master, it was able to read and log up to 64 registers from Modbus slaves. RS485 master is the Master Brick which has a USB, Ethernet or WIFI connection to the PC running brickd. Regardless of the network, however, there are only four signals used: SCK provides a synchronized clock, MOSI and MISO signals are used for data transmission and reception, and /SS configures the QScreen as a master or slave device. The QScreen Controller, however, does not implement hardware handshaking. AIR Commander Entire includes standard micro-USB cable for camera connection however, the Marshall connection needs special RS485 adapter cable. Ideally, the two ends of the cable will have a termination resistor connected across the two wires. Specific RS485 connectors may have different pinouts. Either a 4 position terminal block (5mm pitch) or RJ45 connectors can be fitted for the RS-485 connectors. The diagram below shows potentials of the A (blue) and B (red) pins of an RS-485 line during transmission of one byte (0xD3, least significant bit first) of data using an asynchronous start-stop method.

There are surface mount resistor pads on the QScreen that will allow you to bring out the secondary serial port to the Field Header on pins 5-6 or 7-8 as shown with the parentheses in Table 11-3. Pads are also available to bring out the RS485 signals to the DB9 Serial 1 Connector. The QScreen Controller’s kernel software contains a complete set of high level driver routines for the Serial2 port, and these functions are summarized in the Control-C Glossary. Some measuring instruments have bar indicators that show the current level as a percentage of the set full scale. In fact, you have been using it all along as you worked through the examples in this document. If not only the electrical parameters are to be monitored, but also the energy consumption, measuring instruments which also have active and reactive energy metering should be selected. For example, thermochemistry, the study of heat and energy associated with chemical reactions or physical transformations, is a perfect lab experiment application for the Brainchild. The only possible reference is the reading of the displayed value, for example, of the current. The Silence() routine searches the incoming serial characters for a pre-determined keyword (for example, the ascii name of this particular slave).

Page 60 Block Communication Function for LED Display To display LED data for ASCII display that is synchronized to each digit, set data for each digit and validate this set data by display selection by communication (Communication Number FA65). Before digital instruments begin to operate, they must be set with measurement system parameters and communication parameters. In order to ensure that the instrument is properly protected, fuses must always be fitted to the power cables of the digital instruments and to the measurement inputs of the voltmeter. In multifunction instruments, not only the cables connected to the measurement, but also the RS485 serial port and the analog and digital inputs and outputs must be wired. In digital instruments, this indication is not. An optional exclusive color HMI was chosen for local indication and configuration. Configuration and data accessibility were a snap: the FieldLogger's user-friendly configurator software was accessible by Ethernet, USB or RS485, and also provided means for online monitoring, downloading of all logged data, and quick exporting to spreadsheets and other formats.

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