How does it work?

The SV Series operates basically like a normal fixed position bar code scanner. The unit will automatically read a bar code symbol and transmit data for that symbol through its serial port. With the philosophy of also being a verifier, special considerations are incorporated in the scanning operation, plus other features are included to make the SV Series a very flexible system component.

There are three levels to SV operation as described below.

Level 1 - Scanning Operation

This operation is always enabled. When a bar code enters the laser beam, the SV unit “locks” onto it and continues to scan the symbol until it leaves the laser beam. While a bar code is in the beam, the SV unit’s READ led will be on. When the bar code exits the beam, the SV unit performs quality analyses on the code by averaging all the scans gathered while the code was in the beam and transmits the decoded data along with all quality information via the serial communications port.

Special features and considerations of scanning operation vs. normal bar code scanners:

  1. For optimum analysis accuracy, a fixed mounting distance and angle are required therefore depth of field is very small compared to a simple decoding application. This is equivalent to needing a guide attachment on a portable pen based verifier.
  2. The SV can simultaneously scan up to four bar codes across its scan path.
  3. The serial transmission report contains a fixed block of data approximately 88 bytes long that contains all quality analysis information for the symbol that was scanned. This block of quality data is placed preceding the decoded data of the bar code.
  4. Other scanning operations are programmable – contact RJS technical support for details.

Proper system setup is very important. RJS provides ScanVision software for Windows as an easy to use setup and monitoring tool. ScanVision is free of charge.

Level 2 – Output Port Operation

The SV Series has five output ports that can be manipulated by various bar code quality and data parameters. This is accomplished by enabling an output interface mode. An assortment of modes is available. The modes are selected and programmed through serial communications. Each mode has a specific format for output activation and also has a specific list of programmable parameters available to use as conditions to activate the ports. This enables an SV to control a printer, send signals to a PLC, illuminate a light stack, etc.

An example of using the SV Series output ports to stop a thermal printer when an error is detected:

Many thermal printers have I/O ports that allow external devices to stop the printer in order to wait for an external function such as an applicator taking a label then placing it on an object. Some printers need a ground signal to stop, others need the absence of a ground signal to stop. There are a number of output interface modes in the SV Series that provide both signal levels in an error condition. The particular SV output port that provides the proper signal level can be connected directly to the printer input in most cases. When the error condition occurs, the output port level is “latched. ” In order to clear the latch condition and resume printing, the user presses the SV reset button.

An example of using the SV to illuminate a light stack requires two major considerations - the logic and the circuit:

The logic is accomplished by using one of the output interface modes that can activate particular output ports for “good”, “poor quality” and “no read” conditions. Each port can be connected to a particular color of light. The ports are programmable to pulse on for a set amount of time or to latch. In the case of an active light stack, they should be set to pulse at a slightly longer time than the time between objects being scanned and analyzed. This provides a continuous light illumination if analyses are consistent.

The circuit usually requires a device to interface between the SV ports – (open drain FETs that can sink up to 100 ma) – and the type of light being used in the stack. The device most commonly used is a solid state relay.

Level 3 – No Read Detection

Bar code quality and data analyses depend on the symbol being able to be decoded. In many on-line applications, there is a possibility of printer errors, applicator errors, material problems, damaged labels, etc. that cause an unreadable or non-present bar code. This “No Read” condition is very often an important parameter to detect.

SV units detect a No read condition by receiving a synchronization (sync) signal. The SV can be programmed to count the number of codes entering the beam during a sync interval and if all the expected codes are not read, a No Read condition is determined. This condition can manipulate an output port and/or cause a special No Read data transmission to be sent.

Notes regarding sync inputs:

  1. Sync inputs can be generated by sensors, printer/applicator logic, label sensors etc.
  2. A sync input is a background function that the SV uses for counting. Due to level 1 scanning operation described above, all codes going through the beam are always decoded (if they are capable of being decoded) and analyzed. Therefore only the counting of symbols entering the beam in order to determine a No Read condition is dependent on the sync input.
  3. When a sync signal is received by an SV unit, the Power/Sync led will blink from green to yellow for a short period time.

Example of a sync operation:

A sensor can be used to monitor the presence of a box on a conveyor. While the box is in the sensor’s range, the sensor provides a particular sync input to the SV unit and the SV counts the number of codes entering the beam during this time. If the number of codes decoded did not meet the programmed number of codes expected, a No Read condition occurs.

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