Melt pressure measurement has depended on mercury fill for forty years because nothing else coupled the diaphragm to the sensing element as faithfully at 350 deg C. The Zias PT173 retires the mercury with a patented gallium alloy fill and AFT vacuum filling technology, keeping the fast hydraulic response while removing the toxic column from the plant.

Why does filling technology matter more than the diaphragm spec?

A melt sensor spends its life where the screw tip meets molten resin at 300-plus deg C, and any vapor pocket or void in the fill fluid shows up as measurement lag or drift. The gallium alloy fill is non-toxic and non-flammable, legal to ship into jurisdictions following the Minamata Convention, and the vacuum fill process leaves no bubble to compress. Response time stays under 1 ms, fast enough to capture screw-tip pressure ripple, with repeatability of 0.1% FS. Compared with the legacy mercury units from Dynisco and Gefran that many lines still run, the PT173 offers the same 1/2-20 UNF or M18x1.5 mounting as a dimensional swap, so retiring mercury does not mean re-machining the barrel.

What does the internal 80% shunt calibration change at line side?

Zeroing a melt transmitter traditionally meant a calibration lab visit. The PT173 carries an internal reference resistor and a one-key rezero button, so an operator checks the 80% point between resin changes and corrects zero in seconds. Output spans 4-20 mA, 0-10 V and mV/V with an RS485 option, and temperature can ride along through a J, E, K thermocouple or Pt100 in the same stem. Against the rigid-stem PT170 sibling, the PT173 variants cover rigid, flexible capillary and dual-tip layouts for tight die-head access, and the Zias (Shanghai) IOT Technology Co., Ltd. range tops out at 2000 bar for high-pressure compounding where most rivals stop at 1000.