Epe pic magnetometer

[Orbit]

gs2 downloader v2.3.2 software downloadthere is no link! best regards !

[wubian]

Greeting

my question may be a very stupid question but please help me to find the answer.

there is two program files with .asm and .hex extension. please let me know which IC on below schematic need to be programmed with which file?





Regards

[Orbit]

http://www.geotech1.com/forums/attac...7&d=1273632425 maggy 710

[makedonyalı]

PCB, please

[SimonS]

The problem was resolved 10k resistor on nutrition.

I have the same problem. But I don't understand you where to put 10K resistor?
When power ON I look with osciloscope there is no comunication from EEPROM. When I give command to full erase EEPROM comunication work
regards

edit:
No I try again. There is comunication on power ON. But 0 EEPROM CHIP

[SimonS]

.ASM is source file with assembrel
.HEX is compiled file. This is file that you must load it on PIC

[SimonS]

I have the same problem. But I don't understand you where to put 10K resistor?
When power ON I look with osciloscope there is no comunication from EEPROM. When I give command to full erase EEPROM comunication work
regards

edit:
No I try again. There is comunication on power ON. But 0 EEPROM CHIP

Found!
EEPROM at location 1 was defect. I move second one to first location now find 1 EEPROM.

[mrkhrdr]

Ivanic & Haze, Earlier in this thread you should find someone who dismantled an FGM sensor and reverse-engineered a schematic. There are 2 coils wound around some ferromagnetic strips. I think the latter were made of an amorphous ferromagnetic metal - an American mfr is MetGlas. Honewell may own that division and there are other companies that distribute the metal and parts made from it. From the schematic, it appears that the electronics contain only transistor active components to make an oscillator and amplifier. The 2 coils are incorporated in the circuit. This type of probe is an inductance sensor, possibly the simplest magnetometer for a home DIY project. A coil inductor sets the resonant frequency of an oscillator. I've seen somewhere an example using an op-amp oscillator with the coil in the feedback loop. The inductance of the coil is sensitive to the ambient DC field, so the resonant frequency depends on the field strength AND its orientation relative to the inductor core. I suppose a key factor determining the sensor's sensitivity is the oscillator's Q factor. A higher Q means a sharper amplitude/frequency curve and more sensitivity to ambient fields.

[Davor]

Higher Q is mostly responsible for stability and better phase noise. Being so frugal in design, and reportedly may benefit from better voltage stabilisation, I'd say Q factor was not the FGM designers' main concern.

[mrkhrdr]

For a while, I thought that the FGMs were induction probes and said so. Yesterday, I read the Moreland's papers and the Speake documents, which claim that the probes are in fact flux gates. So now I'm thoroughly confused. My understanding of the latter is that while driven by an AC current of a fixed frequency, they return a signal of frequency 2*f. This fact enables the detection of the signal without the driving waveform, and reducing noise as well. Note that since the driving frequency is fixed, the frequency of the sensor signal is not variable, only its amplitude.
Yet the output of the FGM probes themselves are AC currents the frequency (& period) of which depend on the ambient field strength. How is this possible, if the probe is a flux gate sensor? Also, it appears that the Speake chips take the sensor frequencies, convert them to voltages and then to 8-bit digital words (although there is a 12-bit version available). It seems to me that using accurate timing circuitry we could measure a period or frequency more simply and accurately than trying to isolate an AC signal and measure its amplitude. I've read all the documents from Speake and Moreland, I looked through other flux gate literature and I still don't understand these principles as they apply to the FGM sensors. Can anyone explain these things, or at least point me to a relevant source of information?

[Davor]

You could seek articles about self-oscillating fluxgate sensors. They are quite simple relaxation type oscillators.

What I wonder is feedback pin usage - I failed to find any specification, datasheet or schematic that would vaguely explain using a feedback pin. It is obvious that you can wind a compensation coil on top of the FGM, and thus translate it's reading in a more linear zero net field, but that's not explaining the feedback pin existence. Could anyone please supply some information on that feedback pin?

[Krzysztof]

Hi!
Current feedback change point work on the characteristics B/H.
Change insignificantly, looking for a linear space and symmetrical.
Basic work is already close to a well set. The use of feedback is not necessary
Best regards Chris.

[Davor]

Thank you Chris.
Little changes in linearity are not much of a benefit, so you are right - feedback is not necessary.

[mrkhrdr]

Davor, Thanks for the tip about self-oscillating fluxgates; I'll try Google-ing the term. As for feedback, I've seen it mentioned in the applications literature; but there don't seem to be any actual descriptions of relevant circuitry there. As Chris states, it seems to be a rather ineffective in zeroing the sensed magnetic field. An idea I like is using an extra solenoid to create a closed-loop detector, in which a DC current amp samples the sensor output and drives the feedback coil. When the latter nulls the net field detected by the fluxgate sensor, the electronics will lock on that feedback current. That current is then proportional to the ambient field strength. (NB. I'm not an EE. Hopefully the feedback loop won't oscillate. Any comments?). This method has the advantage of keeping the net field around the detector at 0, where linearity is guaranteed.

[Davor]

Loop stability is achieved as in any other closed loop systems. You have to place poles and zeroes carefully if your loop is more complex than 1st order. The linearity in closed loop would improve, allright, but sensitivity would decrease.