The 93 Series is Indumart's pneumatic indicating temperature controller for industrial process loops — operating entirely on 3–15 psi instrument air with no electrical power required, making it inherently suitable for hazardous-area temperature control where electrical instruments would need costly explosion-proof enclosures or intrinsic safety barriers. A stainless steel spiral sensing bulb drives the indication and control output; 13 standard temperature range codes cover spans from −20°C to +400°C with over-range capability of 15–20%.

How do the 8 control modes differ?

The 93 Series offers eight distinct control actions selectable by mode code. Mode 1 provides simple On/Off with 125% output for 1% input change. Mode 2 is proportional-only (P, 2–200% band). Mode 3 adds integral (PI, P: 4–400%, I: 0.1–25 min). Mode 4 is full PID (D: 0.05–5 min). Mode 5 is PD (no integral). Mode 6 is differential gap (1–100% of range). Modes 7 and 8 replace standard integral with rapid integral (IR: 0.05–5 min) — faster reset action for processes with short time constants. The choice depends on the loop dynamics: On/Off for simple thermostatic control, PI for most temperature loops, PID where derivative anticipates fast disturbances, and rapid integral where standard reset is too slow.

How is the temperature range code selected?

Thirteen standard codes (B through R) cover different span and bulb insertion depth combinations. Low-temperature codes (B: −20 to +40°C, C: 0 to +60°C) use a 160 mm bulb immersion depth. Mid-range codes (E through H: 0 to +140°C) use 105 mm. High-temperature codes (K through R: up to +400°C) use shorter 65–110 mm bulbs for thermal protection. Over-range tolerance is 20% for low/mid codes and 15% for high-temperature codes. The bulb is semi-bendable with an adjustable threaded process connection; stainless steel thermowells (threaded or flanged) are available for corrosive environments.

What accessories and options are available?

Optional IP 55 weatherproof enclosure, alarm contacts, lock-with-key security, pneumatic set unit for remote setpoint adjustment, anti-vibration supports, remote diaphragm seal for corrosive or high-temperature applications, integral action desaturator to prevent reset windup, internal or external auto/manual station, external knob for setpoint control, and mounting bracket for 2-inch pipe mounting. An overpressure stop rated at 5× end scale value is available for pressure-sensing configurations.