MS-121

Overview

The Dwyer Instruments MS-121 is a micro differential pressure transmitter designed for measuring low-pressure differentials and air velocity. It features a compact design suitable for wall or panel mounting. The device provides a 4-20 mA two-wire output signal. It supports multiple measurement ranges including 0.1, 0.25, and 0.5 inches water column (25, 50, and 100 Pa). The unit operates on a 10 to 35 VDC power supply. Accuracy is specified at ±1% for the 0.5 and 0.25 inch w.c. ranges, and ±2% for the 0.1 inch w.c. range under standard conditions. Stability is rated at ±1% of full scale per year.

Feature Summary

• Capable of measuring both differential pressure and air velocity
• Features field-adjustable zero and span via digital buttons
• Supports metric and imperial measurement ranges
• Includes optional four-digit LCD display for local monitoring

Applications

• Monitoring filter status in HVAC systems
• Measuring airflow velocity in ducts
• Monitoring cleanroom pressure differentials
• Detecting fan or blower performance

Procurement Notes

Verify the specific pressure range required for the application, as the MS-121 is available in distinct configurations for 0.1, 0.25, and 0.5 inches water column. Confirm that the process media consists of air or non-combustible compatible gases, as other media may affect sensor integrity. Ensure the installation environment remains within the specified temperature limits of 0 to 150°F. Check for the necessity of an integrated LCD display option if local readout is required for maintenance personnel.

Selection Notes

Select the MS-121 when precise measurement of very low pressure differentials is necessary. This model is appropriate for applications requiring a 4-20 mA output for integration with PLCs or DCS systems. Consider this part for installations where space is limited due to its compact form factor. Verify that the expected pressure fluctuations do not exceed the maximum pulse pressure rating of 10 psi to prevent damage to the sensing element.

Part Context

The MS-121 belongs to the Dwyer MS series of micro differential pressure transmitters. This series is engineered for high sensitivity in low-pressure environments. The family includes variants with voltage outputs and different mounting styles, such as pipe mount versions. The MS-121 specifically denotes the 4-20 mA output configuration with wall or panel mounting capability.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.