How does the Hall Effect sensor store data?

po2le

According to the Melexis 90217 Hall-Effect Sensor data sheet, the sensor has an On-chip 10 bit A/D converter and logic that acts as a sample and hold circuit.·

Apparantly the data·(as·pulses) is stored· in digital form.· Does the stored data indicate changes in pulse frequency·over a period of time? (Then converted to RPM)

The info. sheet further states:·Using the Melexis 90217 with a BASIC Stamp requires the use of the COUNT command for a specified duration, as shown in this example:

COUNT SpeedIn, 1000, Pulses
RPM = Pulses * 60

This looks like the sensor could be used to·detect changing RPM data over a period of time - Is this·true?

Patrick

Mike Green

Reading the datasheet, it looks like the two ADCs and the logic are used internally so the switching threshold tracks the magnetic signal from the gear teeth. It doesn't store any information about the rate of the pulses. It simply produces a logic pulse for each magnetic pulse it sees. By counting the pulses over a fixed period of time, the Stamp can calculate the RPM. You can certainly write a Stamp program to track the RPM information over time. The sensor won't do it for you though.

po2le

Thanks, Mike.· Sounds like it·might work for me.· I woulld like to pick up the changing RPM of a motorcycle, over a period of 10 - 15 seconds, while on board the bike.· (Testing the bike over a quarter mile, or from one speed to another)· I want to 'sample and hold', then bring data back to a PC and put the data on a spreadsheet, like excel.· I'm working on it, anyway.