HIRSCHMANN MDA422-1/2-3.5c-23/46 sensor

The MDA422-1/2-3.5C-23/46 is a high-precision industrial melt pressure sensor designed specifically for the demanding, high-temperature environments of plastics extrusion and polymer processing.

Note on Manufacturer: While sometimes listed or distributed alongside industrial connection accessories (like Hirschmann connectors or by specialist automation distributors under matching names), this core sensor is engineered and manufactured by Dynisco, a global leader in extrusion process measurement.

Product Introduction / Overview

The MDA422 series is a liquid-filled melt pressure transducer featuring a rigid stem coupled with a flexible capillary tube. The flexible capillary serves a vital role: it isolates the delicate strain gauge housing and electrical connection from the intense radiant heat generated by the machine barrel or heating bands. This mechanical isolation dramatically extends the sensor's lifespan and maintains measurement stability.

Part Number Breakdown: MDA422-1/2-3.5C-23/46

MDA422: Series identifier (liquid-filled melt pressure transducer with flexible capillary, ±0.5% or ±0.25% FSO accuracy options).

1/2: Process mounting connection — standard 1/2-20 UNF thread.

3.5C: Pressure range of 0 to 350 bar.

23/46: Physical dimensions — 23 cm (9 inches) rigid stem and 46 cm (18 inches) flexible capillary.

Technical Table

Environmental Tolerance Conditions

This sensor is engineered to separate extreme media temperatures from sensitive electrical components.

Maximum Media Temperature (at Diaphragm): Up to 400°C (752°F).

Maximum Housing/Electronics Temperature: 120°C (248°F).

Zero Shift (due to diaphragm temp change): Less than 0.2 bar per 10°C.

Zero Shift (due to housing temp change): 0.2% F.S.V. per 10°C.

Maximum Overload Pressure: 2x rated pressure range without affecting operating data.

Burst Pressure limit: 6x rated pressure range (maximum limit of 3.000 bar).

Operating Instructions

To prevent damage to the delicate diaphragm, mounting thread, or internal fill system, always follow this operational order:

1.Verify Mounting Hole Dimensions：Before installation。

Ensure the mounting hole is completely clean of frozen polymer residue and matches the standard 1/2-20 UNF profile. Use a specialized cleaning tool kit if needed.

2.Hand-Thread and Torque：Mechanical mounting。

Carefully thread the sensor by hand first to avoid cross-threading. Tighten using a torque wrench to a maximum recommended torque of 15 to 20 Ft-Lbs (20 to 27 Nm) to ensure a seal without stripping.

3.Secure the Flexible Capillary：Routing。

Route the 46 cm flexible capillary away from direct contact with machine heaters, sharp edges, or high-vibration spots. Do not bend the capillary tighter than a 1-inch minimum bend radius.

4.Pre-heat the Extruder：Thermal equilibrium。

Never attempt to remove or tighten the sensor when the machine is cold. The polymer must be completely molten (above its melting point) before the sensor diaphragm is subjected to any mechanical force or systemic pressure.

5.Electrical Zero & Calibration：Startup。

With the extruder at operating temperature but at zero pressure, perform the zero balance. Use the built-in 80% internal shunt calibration to match the transducer's output signal to your controller or readout.

Fault Diagnosis

Crucial Rule: Never remove a pressure sensor from a barrel when the surrounding plastic is cold. The frozen polymer can tear the diaphragm completely off the tip during removal.

No Signal / Infinite Resistance:

Cause: Broken Wheatstone bridge or cut cable.

Check: Use a multimeter to verify resistance across excitation pins (should be ~350 $Omega$).

Excessive Zero Shift / Unstable Readings:

Cause: Diaphragm damage (dented or worn away) or moisture inside the 6-pin electrical connector.

Check: Inspect the tip for mechanical wear or chemical etching. Keep the Bendix connector dry.

Constant High Pressure Reading (Even at Zero Actual Pressure):

Cause: The sensor was tightened into solid, un-melted polymer, or the mounting hole depth is too shallow, forcing the diaphragm to bottom out mechanically.

Check: Use a mounting hole depth gauge to verify recess clearance.

Related Models of the Same Series

The MDA4X2 family is highly configurable depending on the mounting space and temperature isolation requirements:

MDA420 Series: Melt pressure sensor with a rigid stem only (no flexible capillary). Best for installations where space is open and radiant heat is low.

MDA462 Series: Flexible capillary model featuring ±1.0% F.S.V. accuracy (alternative option to the MDA422's ±0.5%/±0.25% precision).

TDA432 Series: Combined design incorporating both a melt pressure sensor and a built-in thermocouple or RTD temperature probe at the tip.

Storage Conditions

Temperature Range: Store between -25°C and +85°C.

Atmosphere: Clean, dry, and non-corrosive environments.

Diaphragm Protection: Keep the plastic protective cap on the 1/2-20 thread and tip whenever the sensor is not installed to prevent accidental scratches or impact damage to the DyMAX® coated diaphragm.