Dwyer Series DM DigiMag® Differential Pressure Transmitter

Product Overview

The Series DM DigiMag® Differential Pressure Transmitter senses the pressure of air and compatible gases and transmits a standard 4-20 mA output signal. The DM housing is designed for direct mounting in the same diameter cutout as a standard Magnehelic® gage. It offers a wide range of models factory calibrated to specific ranges. The polycarbonate molded housing features integral pressure connections, reducing installation time. Digital push-button zero and span controls simplify calibration, and a single push-button allows field selection of 4 to 6 engineering units, depending on the range.

Benefits/Features

• Reduced installation time with zero and span controls for quick and easy calibration.
• Fast and easy setup and calibration with push-button zero and span controls.
• Immediate corrective action is possible via the easy-to-read LCD display.
• Reduces upgrade installation costs and simplifies field upgrades from a Magnehelic® gage due to identical cutout diameter.

Applications

• Differential pressure across filters
• Fan control
• Static pressures in ducts or buildings
• Room pressurization monitoring

Specifications

• Service: Air and non-combustible, compatible gases.
• Wetted Materials: Consult factory.
• Housing Material: Polycarbonate.
• Accuracy: ±1% FSO for all ranges except 0.25 in w.c. @ ±2% FSO, and ranges at or below ±0.1 in w.c. @ ±4% FSO.
• Stability: < ±1% / year FSO.
• Pressure Limits: Ranges > 1 in w.c.: 6 psi max operation, 6 psi burst; Ranges ≤ 1 in w.c.: 3.6 psi max operation, 6 psi burst.
• Temperature Limits: -4 to 158°F (-20 to 70°C).
• Thermal Effect: 0.036% FS/°C (0.02% FS/°F).
• Power Requirements: 10-35 VDC (2-wire).
• Output Signal: 4-20 mA (2-wire).
• Zero and Span Adjustments: Push-button.
• Loop Resistance: 0 to 1250 Ω max.
• Current Consumption: 21 mA max.
• Electrical Connections: Screw-type terminals.
• Process Connections: Male ports on side for 1/8", 3/16", 1/4", 5 mm, 6 mm ID flexible tubing.
• Enclosure Rating: NEMA 4X (IP66).
• Mounting Orientation: Not sensitive to position.
• Size: 5" OD (127 mm) x 1.9" (48 mm) deep.
• Weight: 7.04 oz (200 g).
• Agency Approvals: CE.

Installation

Location

Select a clean, dry mounting location free from excess vibration where the temperature will remain between -4 to 158°F (-20 to 70°C). Distance from the receiver is limited only by total loop resistance. See Electrical Connections. The tubing supplying pressure to the instrument can be practically any length required, but long lengths will increase the response time slightly.

Position

Transmitter pressure accuracy is not affected by orientation. If choosing a non-vertical installation, ZERO the unit to remove any offset due to gravity.

Pressure Connections

NOTICE: Two integral tubing connections are provided on the side of the gage. They are sized to fit 1/8", 3/16", 1/4", 5 mm, and 6 mm ID flexible tubing. Ensure the pressure rating of the tubing exceeds that of the operating ranges.

Panel Mount

Provide a 4-9/16" diameter opening in the panel. Insert the gage and secure it in place with the provided screws and mounting lugs.

Diagram Description: Shows a panel mount installation with a circular opening in a panel, screws, and mounting lugs securing the transmitter.

Surface Mount

Provide three 3/16" diameter holes in the panel on a 4-1/8" diameter bolt circle. Cut an opening for the terminal block as shown in the diagram.

Diagram Description: Illustrates a surface mount configuration with three mounting holes arranged in a circle, and a cutout for the terminal block.

Electrical Connections

CAUTION: Do not exceed specified supply voltage ratings, as doing so will result in permanent damage not covered by warranty. This unit is not designed for 120 or 240 V AC line operation.

Electrical connections are made to the terminal block located in the back of the transmitter. Terminals are marked + and COM.

Diagram Description: Shows a close-up of the terminal block with '+' and 'COM' markings for electrical connections.

Wire Length

The maximum wire length connecting the transmitter to the receiver depends on the wire gauge and the receiver's resistance. For calculating loop resistance, wiring should not contribute more than 10% of the receiver resistance. For runs over 1000', choose a receiver with greater resistance. When wiring length is less than 100', 22 AWG wire can be used.

2-Wire Operation

An external power supply delivering 10-35 VDC with a minimum current capability of 40 mA DC (per transmitter) is required to power the control loop. Refer to Figure 4 for connection of the power supply, transmitter, and receiver. The range of appropriate receiver load resistance (RL) for the DC power supply voltage is expressed by the formula and graph in Figure 5. Shielded two-wire cable is recommended for control loop wiring. If grounding is required, use the negative side of the control loop after the receiver.

Diagram Description (Figure 4): A schematic showing a 2-wire loop with a Power Supply (10-35 VDC), Series DM Pressure Transmitter, and a Receiver connected in series.

Diagram Description (Figure 5): A graph illustrating the relationship between Total Receiver Resistance (Ohms) and Power Supply Voltage (V). The graph shows an operating region for the transmitter, with a maximum value of 1250 Ohms.

Select Unit of Measurement

To select a unit of measurement, press and release the UNITS button to cycle through the available options. The LCD will display the currently selected unit.

Calibration

To calibrate the transmitter, you will need three pieces of equipment:

1. A calibrated pressure source capable of generating a stable pressure value for the maximum range of the unit under test.
2. An instrument capable of validating the calibration pressure.
3. An ammeter capable of measuring the current mA output from the unit under test.

The transmitter is calibrated using the following procedure.

Preparing for Zero Calibration, Span Calibration, Response Time Calibration, or Restore Factory Calibration Coefficients

To prepare the unit for zero or span calibration, response time calibration, or to restore factory calibration coefficients, follow these steps:

1. Connect the ammeter and power supply, observing polarities.
2. Press both the ZERO and UNITS buttons simultaneously for 6 or more seconds, or until "CAL" is displayed. Release both buttons.
3. The units indicator on the LCD will blink on and off, indicating the gage is ready for calibration or restoration of coefficients. The unit's indicator will blink for approximately 10 minutes, then stop blinking.

Zero Calibration

• Apply zero pressure to both ports.
• Press the zero button for 3 seconds. Release.
• The zero function will be processed 3 seconds after the button is released.
• The display will read "2Er" and then sequence back to the home display.

Span Calibration

NOTICE: For a positive span, apply pressure to the positive "+" port.

The span calibration function allows the pressure value to be adjusted so that the currently applied pressure matches the maximum configured pressure. This sets the maximum analog output at the set pressure. It is recommended that the ZERO function be applied before performing a span calibration.

• Apply the maximum desired pressure to the device.
• Press and hold the UNITS button for 3 seconds.
• The span function will be processed 3 seconds after the button is released.
• The display will read "SPA" and then sequence back to the home display.

Response Time Calibration

Press both the “ZERO” and “UNITS” buttons simultaneously for 3 seconds to toggle between fast (0 seconds) and dampened (4 seconds) response. The display will read FST or SLO to indicate which mode is now selected.

Restore Factory Calibration

To restore the gage's factory calibration coefficients:

• Press both the “ZERO” and “UNITS” buttons simultaneously for 6 seconds or until "rSt" is displayed.
• The device will reboot after 5 or 6 seconds.

Maintenance

Upon final installation of the Series DM, no routine maintenance is required. The Series DM is not field serviceable and should be returned if repair is needed. Field repair should not be attempted and may void warranty.

Symbol Description: A symbol indicating that waste electrical products should not be disposed of with household waste. It advises to recycle where facilities exist and to check with the Local Authority or retailer for recycling advice.

Warranty/Return

Refer to "Terms and Conditions of Sale" in the Dwyer catalog and on the website. Contact customer service to receive a Return Materials Authorization (RMA) number before shipping the product back for repair. Include a brief description of the problem plus any additional application notes.

Model Chart

Notes

Blank space for notes.