RPM-8000-PRO offers a discerning solution for automotive RPM measurement without an additional sensor: the practical
instrument is simply connected via a standard jack to the cigarette lighter socket and the RPM is shown directly on the LCD
display. You even have the choice to output the data as an analog voltage (1 Volt per 1000 rev/min) or as a digital pulse
sequence, 1:1 ripple of the alternator (TTL). The smart measuring principle is based on an analysis of the ripple balance of the
supply system, characteristic for all automotive alternators. The frequency (TTL) of this ripple amounts to about 100 to 120
pulses per engine rotation and therefore delivers good dynamic measuring results.
Though the frequency is proportional to the engine RPM, it also depends on the gear transmission ratio from
crankshaft/alternators and on the number of alternators poles and phases. This makes the calibration of the input signal to the
actual measured RPM necessary. The latest version of the RPM-8000-PRO now offers two elegant options:
Internal calibration: The internal calibration assumes a steady engine RPM of 2000 rev/min (drive e.g. in the 2. gear and had
hold 2000 RPM), which can be monitored by the automotive tachometer. By pushing the “Cal. Int” button and keep the button
pressed until the red LED stops flashing, and is permanently illuminated.
External calibration (option): A laser RPM ”RPM-LASER-CAL” is needed for this option. A reflector tag is mounted on the
main belt disc and scanned by laser beam. The TTL output of the laser instrument is connected via cable to the “Ext. Cal In.”
input of the RPM-8000-PRO and delivers one pulse per rotation. (don’t press the “Cal Int” Button for Ext.). By comparing the
pulse sequence with the measured pulse frequency, the instrument calculates automatically the relationship between ripple
balance and speed. Identical displays on laser and RPM-8000-PRO signal successful calibration (also shown by luminescent
LED’s).
The measuring range of the analog output can be varied on demand via jumpers (e.g. to 0.5, 1.0 or 2.0 Volt per 1000 rev/min).
The TTL output can also be scaled with a frequency factor of 1:8 or 1:16 – and therefore adapted to the resolution ability of
attached measuring systems. For software setting purposes, the number of pulses per (e.g. 80-120) revolution is indicated by
pressing the yellow TTL button, independently of the digital output divider (TTL Div). The instrument saves the calculated
calibration data in non-volatile memory until the next calibration.
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