RMI Micro-Monitor

By John R. Shoemaker

The Greek symbol (mu) is used to represent the word micro in electronics, u MONITOR is pronounced micromonitor.

Rocky Mountain Instrument, 202 Fremont Street, Thermopolis, WY 82443, (307) 864-9300 manufacturers this slick, panel mounted aircraft engine monitor that offers a wealth of information in a very small package standard radio stack width (6.253 x 3.25"h x 4.5"d and weighing only 1.5 lbs). Information is presented digitally on a custom liquid crystal display screen. "Oh-oh," you might say, "Can't read that kind of display in direct sunshine." Not so! The aviation green, electro-luminescent backlight display is sharp and legible in bright sunlight and just as easy to read on the darkest night. A front panel activated variable backlight adjustment allows for ambient lighting extremes. Placement of the radio stack in N883RV RVGA is to the right of center with the MONITOR on top. Visibility/legibility is excellent. From a standpoint of readability, the MONITOR rates a 'ten'.

Features abound. Starting with the clock, you can display any one of the following: GMT, LMT, TIMER, FLIGHT TIME, 8 TACH TIME. All, excepting the latter, are easily adjustable by the pilot and appear bottom dead center on the screen.

GMT and LMT are self explanatory.

The TIMER, however, is a little more sophisticated in that it can count up or down, be stopped and restarted, or be used to count down from a number of minutes preset by the pilot. Fuel management is a snap with this feature. For example: set the timer at 30 minutes and start it counting with your takeoff roll; it will count down. When zero is reached, an alarm sounds in both the cabin and headsets, plus the clock portion of the display flashes. This is your audio AND visual notice that 30 minutes has elapsed and it is time to change fuel tanks. The counter immediately starts to count up. Both audio alarm and display flashing will cease when you press the appropriate button. The counter continues on its way toward 60 minutes, at which time the process repeats itself. You have been apprised that one hour has elapsed since the last change of fuel tank. Time to change tanks again. Since fuel management (read 'keeping time') is one of the sticky problems in general aviation, the micro-MONITOR goes a great way toward automatically reminding the pilot that 'time flies'!

The FLIGHT TIME feature is activated by oil pressure and provides a convenient way to record log book time. One might consider zeroing this particular function with every refueling??

TACH TIME is based upon (an adjustable) engine RPM-as is the case on standard tachometers.

Readings for tachometer, pressures (oil and fuel), temperatures (oil, OAT, CHT, EGT & carburetor), ammeter and voltmeter are also digitally displayed by the microMONITOR. A readout of your RPM appears in the top center section of the screen changing in increments of 10 RPM. The readout changes as anticipated with excellent reliability.

Transducers for alarms, fuel and oil pressures, sensors for alternator current, oil and outside air temperatures, and manuals for assembly, installation and usage are all part of the basic package. Some sensors must be assembled by the builder and since your editor burns his thumb on the soldering iron, they were fabricated by a local electronics technician.

Optional transducers, i.e., those not supplied with the basic MONITOR package include: EGT, CHT, Carburetor Temperature, Manifold Pressure and Fuel Flow providing fue flow, fuel quantity remaining based on actual used and endurance based on current fuel flow and fuel remaining). Specific suggestions for type, availability and cost accompany the instructions.

All-in-all there are 22 different functions available. Just think of the panel space that can be saved! Measurements of all critical functions are compared to alarm set points that are adjustable by the user from front panel controls. Out-of-limit measurements automatically activate the audio and visual alarms.

Installation instructions are first-rate and if you are so inclined, the MONITOR is available in kit form (save about $300) as well as a completed product. $1,269 was your editors outlay for a factory built instrument.

Ron Mowrer, owner of Rocky Mountain Instrument, is a straight shooter, easy to converse with and responds to written inquiry promptly thereby providing the kind of factory backup we all applaud and encourage. Warranty is for a period of two years and covers defects in materials and workmanship.


(The above unedited article (except for format) appeared in Van's Air Force - Tri-State Wing, February 1994, 700 South Lafayette, Macomb, IL 61455-2954)