OVERVIEW
Kit Includes:
• CHT FS Series Cylinder Head Temperature Sensor
-12, 14, or 18 mm ID
• Digital Pyrometer Gauge
CHT Sensor
• 12 mm, 14 mm, or 18 mm ID
• -40 °F to 1832 °F operating range (-40 °C to 1000 °C)
• Response time constant: 500 milliseconds
• Cable is 6 feet long (2 meters)
• Made in the USA
Digital Pyrometer
• Small Size ~ 1" high x 2" wide x 3" deep
• Max temperature "Peak hold" display capture capability
• High set-point alarm with internal relay contact
• °F/°C selectable
DIGITAL GAUGE & CHT SENSPR MADE IN THE USA
Our Cylinder Head Temperature (CHT) Sensors are designed for use in engine test and racing environments.
The flexible stem is made of Inconel, providing resistance to corrosion and high temperatures. We use top quality, long-lasting, high temperature, waterproof potting compound at the probe/wire transition, which prevents moisture from entering into the transition causing shorts. Our wires are FEP insulated to protect from shorting and corrosion.
IMPORTANT DISCLAIMER IF YOU ARE CONSIDERING USING THIS INSTRUMENT IN AN AIRCRAFT:
This instrument is not certified by the FAA. Fitting of this instrument to certified aircraft is subject to the rules and conditions pertaining to such in your country. Please check with your local aviation authorities if in doubt. This instrument is intended for ultralight, microlight, homebuilt and experimental aircraft. Operation of this instrument is the sole responsibility of the pilot in command (PIC) of the aircraft. This person must be proficient and carry a valid and relevant pilot’s license. This person has to make themselves familiar with the operation of this instrument and the effect of any possible failure or malfunction. Under no circumstances does The Sensor Connection or manufacturer condone usage of this instrument for IFR flights.
Options:
TECHNICAL SPECIFICATIONS
PMD1XT series Digital Pyrometer Gauge Technical Specifications:
Number of Inputs: | 1 |
Input: | Type K Thermocouple (default) |
Other Input Types: | J & T thermocouple, RTD, Voltage, mA (user selectable) |
Accuracy: | +/-0.2% of reading (+/- 1°C) |
Display Resolution: | 1°F (1°C) |
LED Display: | Red, 4-digit, 0.275 inch (7 mm high), 0.5 second update rate |
Microprocessor Sampling Rate: | 4 samples/second |
Microprocessor A/D Resolution: | 16 bit |
A/D Accuracy: | +/- 0.2% FS +/- 1 unit |
Environment: | 0 to 50C, 85% Max. RH (non-condensing) |
Operating Temperature: | +32 to +125°F (0 to +50°C) |
Front Bezel Rating: | IP51 |
Input Voltage: | 10 to 16 VDC (24 VDC powered available upon request) |
Current Draw: | < 100 mA @ 24 VDC |
Alarm Relay Contact Rating: | 1A @ 30VDC |
Case Dimensions: | 1" x 2" x 3" (24mm x 48mm x 75mm) |
Panel Cutout Dimensions: | 1.77" x 0.87" (45 x 22 mm)(1/32 DIN) |
Weight: | 2.1 ounces |
CHT-FS-K series CHT Sensor Specifications:
Thermocouple type: | Type K |
Accuracy: | +/-0.4% of reading or about +/- 1.1°C (Special Limits of Error) |
Operating Temperature Range: | -40 °F to 1832 °F (-40 °C to 1000 °C) |
Response Time: | 500 mS |
Stem & Ring Terminal: | Flexible Stem Length is 6 inches (152 mm) |
Cable: | Stainless steel over-braid cable with FEP insulated conductors, 6 feet |
DOCUMENTS & DOWNLOADS
VIDEOS
About - PMD1XT + CHT-FS Kit: Digital Pyrometer Gauge with Flexible Stem Cylinder Head Temperature Sensor
This kit pairs the PMD1XT digital pyrometer gauge with a CHT-FS flexible stem cylinder head temperature sensor. The sensor installs under a spark plug and measures the temperature of the cylinder head at the plug boss—one of the most direct indicators of combustion and cooling behavior.
The PMD1XT displays the reading with 1°F resolution, stores peak temperature, and activates a relay alarm when a programmed setpoint is exceeded.
Why Cylinder Head Temperature Matters
Exhaust gas temperature (EGT) and cylinder head temperature (CHT) provide different types of information.
- EGT reflects combustion conditions (air/fuel ratio, timing)
- CHT reflects the thermal load absorbed by the engine structure
CHT is primarily used for:
- Engine protection
- Monitoring cooling effectiveness
- Detecting abnormal thermal conditions
On air-cooled engines, CHT serves a similar protective monitoring function to coolant temperature in liquid-cooled systems.
CHT-FS Sensor: Flexible Stem Design
The CHT-FS uses a flexible Inconel stem:
- 6" length
- 0.062" (1.6 mm) diameter
- MgO insulated
- Pre-bent at ~67°
The flexible stem allows routing around fins, boots, and obstructions commonly found around spark plug locations.
Copper Ring Terminal
The copper ring terminal provides the thermal interface between the cylinder head and the thermocouple.
Copper’s high thermal conductivity allows efficient heat transfer into the sensing junction. Proper seating of the ring under the spark plug is critical for accurate readings.
Flexible Stem Durability
The Inconel stem is durable and designed to be formed during installation.
The stem should be bent into position once and left in place. Repeated bending in the same location should be avoided.
The probe-to-wire transition is sealed with a high-temperature compound to protect against contamination and moisture ingress.
Sensor Specifications
- Type: Type K thermocouple
- Temperature Range: -148 to 1832°F (-100 to 1000°C)
- Accuracy: ±0.4% of reading or ±1.1°C
- Response Time: 500 ms (time constant)
- Stem: Inconel, 0.062" OD
- Junction: Ungrounded
- Ring Terminal: Copper
- Lead Wire: Stainless overbraid with Teflon™ insulation, 24 AWG
Response time is defined as the time required to reach 63.2% of a step temperature change.
PMD1XT Gauge
The PMD1XT is a digital panel meter designed for thermocouple measurement.
- 4-digit LED display
- 1°F / 1°C resolution
- 0.5 second update rate
- ±0.2% of reading accuracy
Within typical CHT operating ranges, this corresponds to approximately ±1–2°F accuracy.
Peak Hold
The gauge stores the maximum recorded temperature, allowing post-run review without continuous monitoring.
Alarm Relay
- 1A @ 30 VDC relay output
- Programmable setpoint
- Stored in non-volatile memory
Compatible with:
- Audible alarms
- Warning lights
- Control circuits
Optional Analog Output
Optional 0–5 VDC output provides a signal proportional to measured temperature for DAQ or ECU integration.
Wiring
Type K polarity must be observed:
- Yellow = Positive (+)
- Red = Negative (–)
Incorrect polarity results in inverted readings.
Installation Overview
Install the ring terminal under the spark plug and torque to specification.
Route the stem and cable away from heat and moving components. Secure using appropriate clips or ties.
Applications
- Aircraft (experimental)
- Karting and racing
- Snowmobiles and ATVs
- Marine engines
- Small industrial engines
Summary
The PMD1XT + CHT-FS kit provides a complete solution for monitoring cylinder head temperature.
- Direct measurement at spark plug boss
- Flexible installation
- High accuracy and fast response
- Integrated display and alarm