The Sentinel Chart Recorder is a microprocessor-controlled recorder which continuously monitors the output of one, two or three industry standard sensors and provides a permanent trace of the results on a rotating, removable chart. Up to 6 relays are available, each independently configurable to provide full alarm and process control. Operation of the chart recorder is via a five-function keypad with associated 2-line liquid crystal display (LCD). A bank of 6 light-emitting diodes (LED’s) provide a quick visual indication of the status of the relays.


  • The Sentinel range of microprocessor-based circular chart recorders is available in 1, 2 or 3 channel variants.
  • Sentinel combines the simplicity and clarity of pen drawn traces together with the versatility of microprocessor control.
  • Each channel is equipped with a universal signal input which is compatible with all industry standard sensors and signals including thermocouple types J, K, T, E, N, R, S and B, Pt100 platinum resistance temperature detectors and 4/20mA current loops.
  • Low and high measurement ranges are provided for each input type, separate range cards are not required. Multi input versions include optoelectronic isolation of the input stages to eliminate troublesome installation ground loops.
  • Thermocouple and RTD characteristics are fully linearised by means of software. In addition thermocouple measurements benefit from automatic cold junction compensation which uses software correction in conjunction with a stable platinum resistance detector for cold-junction temperature sensing.


Number 1, 2 or 3
Input Signals (Standard) Thermocouples K, T, J, N, E, B, R & S
Platinum RTD (Pt100) 3-wire
DC voltage ±2V, +20V
DC current ±2mA, ±20mA
Temperature Ranges Thermocouples to BS4937 (type B minimum temp 200°C) RTD to BS1904:1984
High and low measurement ranges for each input
Cold-Junction Compensation Automatic, using Pt1000 temperature detector and software correction
Linearisation Automatic software linearisation to BS4937 (thermocouples) and BS1904: 1984 (RTD)
Input Resistance T/C: 10 Mohms
±2mA : 200 ohms
±20mA : 20 ohms
±2V, +20V: >1 Mohms
Minimum Span 5°C (Thermocouples K, J, T, E, N & RTD)
Thermocouple Burn-out Pull-up or pull-down, link selectable
RTD Current 1mA approximately
RTD Lead Resistance 3-lead connection, compensated up to 10 ohms maximum per lead
Input Protection ±50Vdc on signal inputs
Input Isolation Optoelectronic on 2 and 3 input versions 500Vrms channel-to-channel, 500Vrms channel-to-earth