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Sensor Synchronization: A Step-by-Step Guide

SYNC Control Guidelines

SYNC mode is useful to prevent cross-talk between sensors in close proximity. The simplest configuration has one master and one slave sensor, a common situation when two sensors are used in one machine such as a converting slitter-rewinder. Larger SYNC groups can have up to 31 slave sensors that can be organized in up to five time slots (phases). In applications with multiple sensors, such as measuring across a conveyor belt to determine material flow volume, using multiple phases assures the sensors are properly spaced in both position and time to prevent crosstalk. A SYNC group has ONLY ONE master sensor, which measures on phase 1 and can be configured to provide slave commands from one to five phases.

Each slave is configured to measure on one of the phases. If only one phase is used the master and the slave sensor(s) will measure simultaneously (assuming the slave sensor(s) is configured for phase 1). If more than one phase is used, as determined by the master sensor, each slave sensor must be configured to one of the operational phases. Two-phase configuration can be set with either the sensor push-button or SenixVIEW software. SenixVIEW must be used to set 1, 3, 4 or 5 phase setups.

Up to 32 sensors can be connected in a master-slave network. When a master is operational, SYNC mode consumes the serial data network and Modbus serial data communications by external means such as SenixVIEW is not possible, but the analog and switch outputs function normally and update at each sensor’s phase time. If the master sensor is disconnected or taken out of master operation the slaves will stop measuring. Slaves that lose the master input can have their analog and switch outputs assume default states as defined by SenixVIEW’s “No SYNC” parameter value for each output.

A more useful benefit of disabling the master is that Modbus communications is restored to the group. SenixVIEW can then connect with all sensors in the SYNC group using the Group Control feature. In fact, Group Control will automatically suspend the master sensor so that the entire sensor group can be configured, saved and/or restored from a backup. These capabilities are possible if all the sensors in the group are first configured with individual Modbus addresses.

The serial data bus configuration of all sensors in SYNC mode is RS-485, whether using an RS-485 or RS-232 sensor model. We recommend using RS-485 sensor models for simplicity and to avoid the need to switch data interfaces when using RS-232 sensors in different modes. The RS-232 models will revert to RS-232 if a sensor’s SYNC function is deactivated.

The more phases in play, the slower the overall measurement function since the master has to instruct all phases in succession. The Measurement Interval value determines the rate at which the master controls the phases. General guidelines:

  • Every sensor in the SYNC network should have its own network address within the range of 1-247
  • All sensors must use the same BAUD rate
  • The SYNC network operates on RS-485 communication protocol
  • All sensors in an RS-485 network have their yellow and gray wires connected (bussed)
  • All sensors must share a common ground (blue) wire

Step-by-step instructions for using the SYNC feature in a network.

a. Determine which sensor will be the master. Connect only it to the PC using SenixVIEW.

b. Determine the network address it will have. All new sensors are at address 1.

c. Under the menu item Sensor choose Communications. There you can assign a new address in the range of 1-247 inclusive.

i. SenixVIEW will disconnect and reconnect at the new address.

d. Navigate to the Measure tool screen. Under “Measurement Activation” choose the SYNC Master that matches the number of phases you intend to use. For example:

i. If you want all sensors firing at one time, choose “SYNC Master 1-Phase”.

ii. If you want your sensors grouped to measure in 4 groups, choose “SYNC Master 4-Phases”.

iii. If you want your sensors to measure in a repeating sequence, such as 123-123-123, choose “SYNC Master 3-phase”.

iv. Do not choose a SYNC Master phase less than the number of phases you intend to have.

e. Close the Measurements tool dialog. You will see a warning screen advising you that if you are connected to an RS-232 sensor it is about to become RS-485 and you will lose the ability to communicate unless you switch to RS-485 style interface equipment. This is why it is better to begin with all RS-485 sensors. To return a sensor to its default (non-SYNC) configuration, see section H below.

f. Disconnect the master sensor from SenixVIEW.

a. Connect to a sensor which will become a SYNC slave using the proper equipment (RS-232 or RS-485 according to its label). The sensor should be the ONLY sensor on the network at this point.

b. Set its network address as above.

c. Choose its SYNC slave phase.

i. Choose a DIFFERENT network address for each sensor. No duplicates allowed.

i. On the Measurements tool dialog, pull down “Measurement Activation” and choose the slave phase.

ii. Choose 1 if you want it to measure in phase 1 with the master.

iii. Choose 2—5 if you want it to measure at one of the alternate phases.

iv. Don’t choose a phase number higher than the master phase number or it will never measure.

d. Close the Measurements tool dialog. Observe the warning screen noted above in 1) e.D.

e. Disconnect the slave from SenixVIEW. Remove sensor from the network.

f. Repeat steps F—I for each slave.

i. Do not duplicate a network address.

a. Wire all network sensors together. This can be done by wiring between terminal boards with shielded twisted pair cable.

i. Connect the slave sensor gray wires together.

ii. Connect slave sensor yellow wires together

iii. The blue reference (GND) must also be extended to every sensor

iv. Connect the Master’s gray, yellow, and blue to the network

v. Every sensor must have a unique network ID at this point and be set for the same Baud rate. If not, see section H

vi. Connect the PC to the network using RS-485 interface equipment

b. Make any regular analog output connections to external equipment as needed.

a. Supply 15-30VDC to every sensor

c. All sensors begin once powered. Slave sensors are triggered by the Master only

d. No serial data communication is possible using SenixVIEW because the Master controls the bus

e. Analog and switch outputs are active while in SYNC mode

f. The SYNC’d sensor group will operate in SYNC mode.

g. While in SYNC mode, individual communication is not possible unless the “Master SYNC OFF” button is clicked. See the following section

a. Open SenixVIEW>Sensor> Group Control

b. In Group Control, click “Master SYNC OFF”.

c. In the Connect dialog box, enter the Network Address of any sensor in the group.

d. Click Connect. Import the sensor setup to the Workspace when asked.

e. Make any changes to the sensor while in the Workspace. Upload the Workspace to the Sensor by right-clicking the WorkSpace icon and dragging it over the Sensor icon.

a. Open SenixVIEW>Sensor> Group Control

b. Using RS-485 communication equipment, do a Scan for Sensors to display every sensor on the network and its address. Every sensor in the group should be displayed in the Sensor List area by address and configuration.

vii. If not, check wiring and review network addresses. No duplicates allowed.

viii. A slave blinking red/green is not in communication with a master.

ix. Only RS-485 sensors will be displayed.

x. Click “Master SYNC ON” to restart the synchronized mode operation led by the SYNC Master.

a. In Group Control, click “Master SYNC OFF”.

a. Stop SYNC operation, as above

b. Connect to the selected sensor using RS-485 communication equipment

c. Navigate to the Measurements dialog and choose “Continuous” from the Measurement Activation

d. Close the Measurements dialog and upload the Workspace to the sensor.

e. Note: Any RS-232 sensor that had been automatically changed to RS-485 while in SYNC mode pull down menu will automatically revert to RS-232 at this time. It will communicate using RS-232 communication equipment

a. On a push-button model, use a TEACH-15 command

  1. i. Unlock the TEACH mode by holding the button for 3 flashes and releasing
  2. ii. LED will flash slowly indicating TEACH mode invoked
  3. iii. Hold the button for 15 flashes then release to cancel SYNC master or slave mode
  4. iv. Hold button for 3 flashes and release to stop TEACH mode, or cycle power, or simply wait 15 minutes

a. Any RS-232 sensor that had been automatically changed to RS-485 while in SYNC mode will automatically revert to RS-232 at this time. It will communicate using RS-232 communication equipment

b. Remove any RS-232 sensor from the network. RS-232 only supports one sensor at a time.