Understanding the Status Inputs for DRIVE+ and LINK+

Understanding the Status Inputs for DRIVE+ and LINK+

To operate correctly, both the DRIVE+ and LINK+ devices need to receive a few simple electrical signals from your air compressor. These signals let the devices know whether the compressor is ready, running, onload, or in an alarm state. In most cases, there are four inputs used — though only three are strictly required.
This article explains each of these Status Inputs in plain terms, including what they do, how they work, and a few different ways you can connect them based on your setup. We’ll also touch on some unique differences between DRIVE+ and LINK+, especially when it comes to Status Outputs.
If you need extra help visualising the wiring, take a look at our Connection Examples.

Ready Status Input

The Ready Input tells the DRIVE+ or LINK+ that the air compressor is healthy and available. It doesn’t matter whether the compressor is currently running or not — just that it’s free of shutdowns or fault conditions. A Ready state is intended to indicate that the compressor is in a ‘started’ state (somtimes also referred to standby, or auto), has no operational inhibiting fault condition and is ready to respond to external regulation without manual intervention.

This input is voltage-activated:
If it sees a voltage between 24–240V AC or DC, it’s considered ON. No voltage means it’s OFF.

Warning
Never apply more than 240V to this input.

How to connect it
There are a few common ways to connect the Ready Input:
  • From a digital output on the air compressor controller
    This output typically goes high when the compressor is in a “good” state (not in fault or shutdown).
    → Used in Example 1 and 2 (DRIVE+ / LINK+)

  • After the emergency stop button
    Wiring it this way ensures that if the E-stop is pressed, the Ready signal is removed.
    → Used in Example 3 (DRIVE+ / LINK+)

  • Any energized circuit that only powers up when the compressor is ready
    This could be a contactor coil or a controller terminal — anything reliable that reflects the compressor’s readiness.


Running Status Input

The Running Input lets the system know that the compressor’s main motor is actively running. Whether it's running under load, spinning in offload or idling, this signal should turn ON.
Like the Ready Input, it’s voltage-activated between 24–240V AC/DC.
Warning
Again, don’t exceed 240V on this input.

How to connect it
Here are some typical ways to connect this input:
  • Across the main motor contactor coil
    When the main motor contactor is energized, this input will turn ON.
    → Used in Example 1 (LINK+)

  • Across the run signal coil of a VSD (Variable Speed Drive)
    Similar to the motor coil, this tells the DRIVE+ the motor is active.
    → Used in Example 1 (DRIVE+)

  • Via a TRIAC output and auxiliary relay
    Some compressors use TRIAC outputs, which can’t be wired directly. Instead, use an auxiliary relay that closes when the TRIAC output is active. If you're unsure if your air compressor uses TRIAC Outputs, you can always use this article to get more information about it.
    → Used in Example 2 (DRIVE+ / LINK+)

  • From a digital output
    A digital output that activates while the compressor is running can also be used.
    → Used in Example 3 (DRIVE+), also applicable for LINK+

  • Across the fan motor coil
    If the fan motor only runs when the compressor runs, this is a useful signal source.
    → Used in Example 3 (LINK+), can also be used for DRIVE+

If none of these options are available, any circuit that only energizes while the air compressor is running will do the job.


Onload Status Input

The Onload Input is used to detect when the air compressor is actually delivering air — in other words, when it’s under load.
This input also works with 24–240V AC/DC, and it's ON when that voltage is present.
Warning
Never apply more than 240V to this input.

How to connect it
You have several options depending on your compressor:
  • Across the coil of the load solenoid valve
    This is one of the most direct ways to get an accurate load signal.
    → Used in Example 1 (DRIVE+ / LINK+)

  • Via a TRIAC output and relay
    Same principle as above — a TRIAC signal switches an auxiliary relay that provides voltage to the input. Again, if you're unsure if your air compressor uses TRIAC Outputs, you can always read this article to get more information about it.
    → Used in Example 2 (DRIVE+ / LINK+)

  • From a digital output
    If your controller has an output that activates during onload, it’s perfect for this input.
    → Used in Example 3 (DRIVE+ / LINK+)

Alternatively, any circuit energized when the compressor is onload will work fine.


Alarm Status Input (Optional)

This one is optional but useful. The Alarm Input helps DRIVE+ or LINK+ indicate when the air compressor is in a fault or warning condition.
It’s again voltage-detecting, with a range of 24–240V AC/DC. If a fault occurs and voltage appears on this input, the device will recognize that an alarm is active.
Warning
Once again, never apply more than 240V to this input.
​
How to connect it
You might choose to connect this in one of the following ways:
  • Across the fault lamp
    If your compressor has a fault indicator light, this is a simple and effective source.
    → Used in Example 3 (DRIVE+), also works for LINK+
  • From a controller’s digital output
    If the controller outputs a signal during alarms, you can use this to drive the input.
    → Used in Example 1 & 2 (DRIVE+ / LINK+), and 3 (LINK+)

As with other inputs, anything that only turns on during a fault will work.
You don’t need to use this input for basic functionality, but it adds helpful feedback to your monitoring setup.

While the DRIVE+ relies purely on pressure manipulation, the LINK+ is a little more advanced. It includes Status Outputs - signals that the device actively sends out. These outputs can be used to control other components, like starting or stopping compressors, based on the system’s real-time status.
The Metacentre Core management system takes charge of these outputs. It automatically controls the LINK+ load/unload relay outputs based on your configured system pressure set points. This means the system knows when to signal compressors to load or unload without manual intervention.
For air compressors that support ‘Remote/Local Pressure Regulation’ via digital inputs, the LINK+ provides additional flexibility. It includes:
  • A Volt-free contact  for load control
  • A Volt-free contact for enabling remote pressure control
This setup lets you switch the compressor’s load regulation from its own internal control logic to a remote signal, allowing centralized control through the LINK+ and Metacentre Core - a powerful way to synchronize multiple assets efficiently. Bellow you can see how you can interconnect your air compressor with these Outputs.





Recap

Here’s a quick summary of the inputs:
  • ✅ Ready Input – Required. Indicates the compressor is healthy and ready to run.
  • ✅ Running Input – Required. Indicates the compressor’s main motor is running.
  • ✅ Onload Input – Required. Indicates the compressor is under load and delivering air.
  • ⚠️ Alarm Input – Optional. Indicates a warning or fault condition is active.
Each input can be wired in multiple ways, depending on the compressor’s available outputs or control signals. The key is choosing a source that reliably reflects the state you want to detect.

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