How to use Analog Sensors to Detect Machine Activity

For machines that do not have obvious outputs that indicate that the machine is running (or a supported PLC where that data is likely to exist), an analog sensor might be required. We would typically use a current loop sensor that is wrapped around the power of the Axis or motor that indicates the machine is running. You might need to install multiple sensors if there are multiple motors/systems that can independently be running.  

The sensor we often recommend is the ACT050-10-S AC Current Transducer which can be purchased directly from MachineMetrics, Automation Direct, or your favorite electrical supplier.

The AcuAMP AC current transducer is a fixed core, 0-10, 0-20, or 0-50A selectable sensing range, true rms, 4-20mA output which will work for most applications. Check the machine technical manual to check what the current draw is of the motor just to be sure.

Also required is a MachineMetrics Edge with a Labjack U3 for installation inside the machine, or a Labjack T4 with a 24V to 5V power converter if you are using the MachineMetrics Edge (Gateway) to connect multiple machines over ethernet. 

Follow the I/O Installation guide that describes how to configure a machine with Digital I/O with relays, except replace the relay with the Current sensor. The two terminals on the AccuAmp should be connected to a ground (GND) pin and any AIN pin on the MachineMetrics I/O device. The polarity (+/-) on the AccuAmp does not matter as the signal we are using is AC.

Your configuration script will look like this, with the output on the sensor connected to PIN 0:

device: labjack-u3
input:
  digital:
    spindle_1:
      pin: 0
      v-threshold: 3
data-items:
  execution:
    value:
      ACTIVE: spindle_1
      READY: true

If there is more than one sensor required, you will need to use logical operators to combine each sensor into one signal that indicates the machine is running. 

device: labjack-u3
input:
  digital:
    xaxis:
      pin: 0
      v-threshold: 3
    spindle_1:
      pin: 1
      v-threshold: 3
data-items:
  execution:
    value:
      ACTIVE: xaxis or spindle_1
      READY: true