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Howell Instruments H1900

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Primary Display Options:

  • Engine Speed
  • Engine Temperature
  • Engine Torque
  • Engine Pressure Ratio (EPR)
  • Fuel Flow/Pressure
  • Oil Pressure/Temperature
  • OAT
  • DC Voltage

Available Monitoring Functions include the options listed above as well as:

  • Identification and Usage Data including:
    • Aircraft/Engine Number
    • Engine Starts
    • Engine Hours
    • Engine Cycle Counting (Low Cycle Fatigue)
  • Hot Section Exposure
  • Exceedance Data
  • Trend Data Howell Instruments


Power Input 28 VDC nominal, 18 to 32 VDC requires 10W maximum.
Case The H1900 Series is 5.5 inches overall length/5.25 inches behind bezel. Both dimensions exclude the input connector.
The H1900 case conforms to MS33639 standard, and supplied in a 2 or 3 inch diameter case.
Mounting MS28042-1 clamp or
MS28055-11 bezel
Weight 1.25 lbs
Environmental DO-160C and MIL-STD-810

Signal Input

  • One low-level DC input used to measure the output of the engine thermocouple harness. ANSI Type K thermocouple, range 0 to 1200 °C.
  • Two frequency inputs usually assigned to monitor engine speed. Inputs from 5 Hz to 20 KHz, 500 mV to 50 Vrms, range 5.0 to 120 %RPM.
  • Two discrete +28 VDC or 28V return inputs that can be used to monitor switch closures from weight-onwheels or bleed air switches.
  • One analog 0 to 5 VDC, usually used to measure a signal from an amplified pressure transducer, for torque, EPR or PAMB.
  • RS-232 input used for data uploading.

Signal Output

  • One discrete +28 VDC or 28V return ouput that can be used to operate a caution panel or other warning device (limitation of 350 mA).
  • RS-232 output used for data downloading.

Optional Input/Output

While many options are available, the most common are listed below:

  • ARINC 429
  • MIL-STD-1553B
  • One resistance input (RTD) for measuring outside air temperature sensors.
  • One synchro transmitter input for measuring engine pressure ratio (EPR) or inlet guide vane (IGV) type devices.
  • One analog 0 to 5 VDC output.

Data Retrieval

  • Two remote-mounted switches allow the operator to step through real-time secondary displays and interrogate or reset stored engine exceedance, usage or performance data. Password protection is available.

  • Download data via the RS-232 output and optional download cable. This option will allow customer specific data to be transferred from the indicator to a PC or Laptop computer in a standard ASCII format. Customer-specified formats available at additional cost.

Special Features

  • Re-programmable through the connector via software and RS-232.
  • Calibration on condition, without opening the indicator.


  • A precision micro-stepper motor drives the analog pointer.
  • The digital display features four, seven-segment LED characters with four decimal points. (NVG compatible per MIL-L-85762A). Brightness automatically controlled via an integral photoelectric cell.
  • Accuracies for the digital display, from –40 °C to +71 °C ambient, ±3 °C / ±0.2 %RPM.

Warning Lamp (Optional)

  • The H1900 Series employs an integral warning lamp, which can be supplied in red, yellow, orange or NVG blue/green or red. Activation point is set to customer specifications.

Ball Flag Indicator

  • Electro-magnetic, latching, ball indicator, password resettable. Normally black, this indicator turns white to indicate an exceedance or maintenance action.

Internal Lighting (Optional)

  • Internal lighting can be provided to operate from 5V AC/DC or 28 VDC system. Brightness controlled by the lighting rheostat in the aircraft. Available color options are white, red, blue/white or NVG.

Connector Interface

  • MS3476W16-26S or PT06SE-16-26S (MIL-C-26482 Series I or II). Adapter harnesses are available to connect to existing aircraft harness, avoiding aircraft wiring change.


  • TSO certification provided depending on application.

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