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DCR-1006A and MNDWe don’t often use this space to feature our products. We try to focus on technologies and general information that are useful regardless of the reader’s relationship with our sensors and controllers. Today we’re going to make a temporary break from that general focus and look specifically at two of our controllers: the DCR-1006A Controller and the MND Modbus Display.

A Tale of Two Controllers: The DCR-1006A and the MND

The easiest comparison to make between the DCR-1006A Controller and the MND Modbus Display is that the DCR-1006A is generally specific, while the MND is specifically general. Makes complete sense, right?

The DCR gives you general control over one specific sensor; the MND displays specific information from one or more (up to 10) sensors. Another way to look at the two is in terms of inputs and outputs: the inputs of the DCR-1006A are constrained to one of three types of sensor, but the outputs are varied and configurable, while the MND can monitor a wider range of sensors, but has very limited output options.

The DCR-1006A Controller is an ideal solution for single tank or sensor monitoring with emergency pump control and remote access. Each DCR-1006A can monitor and control one APG MNU or MPX Modbus sensor or APG DST sensor. However, with four relay outputs and an additional switched input, a DCR-1006A can also be configured to operate a pump in a high- or low-level emergency situation (E-Stop or Start Prevention).

In contrast, the MND Modbus Display is optimal for monitoring and displaying levels from one or more Modbus sensors. An MND can passively monitor sensors on a separately-controlled Modbus system, providing local level displays, it can be used to configure a Modbus sensor, or it can be used as a Modbus Master device for completely independent systems. MND’s can even be configured with a single, switchable power relay output and auto-on/off functionality for regular, timed-interval powered monitoring of a single sensor.


The primary task of the DCR-1006A Controller is controlling and monitoring a single sensor. If an APG MNU ultrasonic sensor or MPX magnetostrictive sensor is used, the DCR and sensor will communicate via Modbus. If a DST ultrasonic sensor is used, the DCR will control the DST via a dedicated port. The DCR-1006A also has one dry contact for switched input.

Compared to the DCR-1006A, the MND Modbus Display has an abundance of input options. Along with the MNU and MPX that the DCR can handle, the MND can monitor LOE ultrasonic sensors, as well as monitor and control PT-400 and PT-500 pressure transducers with Modbus output. The MND can also be used to display the Modbus readings converted by an RST-5003 from a 4-20mA sensor. That is a lot of input options!


Outputs are what set the DCR-1006A apart from the MND. Along with APG Modbus network connectivity, the DCR-1006A also has four SPDT output relays and a 4-20mA output that can be configured based on the readings from the MNU/MPX/DST sensor. The relays can handle up to ¼ HP at 125/250 VAC NC and ⅓ HP at 125/250 VAC NO, and can be independently configured based on eight settings.

Comparatively, the MND output options are limited. Designed primarily for visual display, the MND offers APG Modbus network connectivity, 4-20mA or 0-3 VDC analog output based on the readings of a single sensor, and a choice of one switchable power relay, one SPDT relay, or two NO/NC relays. The 4-20mA analog output and switchable power relay configurations are exclusive of all other options save Modbus connectivity, and even the Modbus functionality of the MND (Master, Slave, or Sniffer) depends on the configuration of the Modbus network.

APG Modbus Functionality

The DCR-1006A Controller is the interface between the sensor it is controlling and the rest of the Modbus network. As such, the DCR appears on the network as a slave device. Modbus registers that configure sensor operation, such as Sensitivity, Pulses, and Gain Control, are applied by the DCR to controlled sensor. Other settings, such as Full Distance, Empty Distance, and Trip Type, are used by the DCR to process the input from the sensor. Because the DCR operates as a slave device on the Modbus network, it is fully configurable using APG Modbus Software on a PC, via an RST-6001 Modbus-to-USB converter, or on an APG-provided website via an LOE or RST-5003 Tank Cloud Master device.

The MND can operate in three modes on a Modbus network: as the Master device of one or more sensors; as a single Slave device connected to a PC running APG Modbus software; or as an invisible Sniffer, displaying readings from one or more sensors on a Modbus network controlled by a separate Master device. None of these configurations allows for an MND to be controllable via Tank Cloud.

So, which one is right for you? As we like to say around here, it depends on your application. For a limited-input, maximum output scenario, it’s hard to beat the versatility of the control options offered by the DCR-1006A Controller. If local display of several sensors is more important, the input flexibility of the MND Modbus Display will be more helpful.

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