LDA Sensor

Hello!

I would like to install an LDA (Light Detection and Ranging) system in my vehicle.
However, I'm stuck in a dilemma when it comes to sensor selection!

If I use a differential pressure sensor like the MPX4250DP, I cannot measure negative pressure (Those who don't understand the point: /viewtopic.php?t=3224)

And with an absolute pressure sensor like the MPX4250AP, the load impact must be corrected. However, atmospheric pressure fluctuates, and therefore the zero point must be adjusted depending on the weather conditions and altitude.

Quote:
The atmospheric pressure at sea level is approximately 1013 mbar on average.
He fluctuates with sea-level weather conditions between approximately 985 and 1035 mbar (absolute extreme values are approximately 880 and 1080 mbar).

What does the practice look like? Do changes in pressure due to weather can be observed on the LDA?

Best regards, Wolfi

[Translating...]was hälst du denn davon:

2 sensoren mit absolutdruck und via differenzverstärker dann den relativdruck zur anzeige bringen.......

[Translating...]

Ja wär schon eine Möglichkeit. Aber leider eine Teure

Viel mehr interessiert mich die Frage wie stark atmosphärische Druckschwankungen auf der LDA sichtbar sind.

[Translating...]

... und warum nimmst du nicht eine analoge mit Zeiger

Die kann LadeDRUCK und -SOG anzeigen und rechnet systembedingt den Aussendruck raus.

m;

[Translating...]

Ist auch war.
Aber ich wollte die LDA an das Zusatzinstrument für die Batteriespannung anschliessen. Bräuchte nur die Skala ändern und eventuell das Signal verstärken.

Bin halt ein kleiner Perfektionist und so würde das wie original aussehen

Hi,

I don't understand the problem.

Take 2 identical sensors, one for external pressure and the other for LD. Then you subtract the value of one from the other using an OP. (Analog calculator)

The result corresponds exactly to the pressure inside the atmosphere.

However, the external pressure does not fluctuate as much due to the weather, but rather due to the altitude. (1 mb per 8m)

This is especially true since the VTG is already not much better than a 50mB reproduction. (Hysteresis)
1mB accuracy is irrelevant.

You will notice that the display becomes very erratic when you display individual mB values, i.e., 4-digit values. However, if you go to 3 or 2 digits, you can save the expensive compensation.


Then you simply connect to the existing LD sensor and thus to your DVM and that's it. (as described in this forum)

garth.brooks wrote:

You will find that the display becomes very nervous if you display individual mB values, for example, 4-digit values.

That's what we want! (As described).

garth.brooks wrote:

Take 2 identical sensors, one for external pressure and the other for LD. Then you subtract the value of one from the other using an OP. (Analog calculator)

I understand perfectly! Joergs has already written it too. However, 2 sensors are not exactly cheap!

garth.brooks wrote:

This is especially true since the VTG is already not much better than a 50mB reproduction.

What does this sentence mean?
Do you mean that the control unit doesn't use a higher resolution? Then, there should always be quite strong charging pressure fluctuations! I just can't quite picture it. But I'm always open to being corrected


I'm just wondering if a change in atmospheric pressure on a pointer instrument is even noticeable.

[Translating...]wieso nicht billig? den vorhandenen ladedrucksensor kannst du anzapfen, und den umgebungsdrucksensor im stg auch. nur darauf achten, daß du daß relativ hochohmig tust. dan den ganzen haushalt subtrahiert und auf ner analogmesse ausgegeben! wo ist das problem? so teuer ist das nicht!

[Translating...]

Damit kommt man aber einem Schadhaften Ladedrucksensor nicht auf die Spur!

[Translating...]ne! das nicht. aber einen kompromiss mußt du schon eingehen! entweder billig und evtl. fehlerhaftet oder teurer und sicherer.... (obwohl die teurere lösung auch fehlerhaft sein kann)
2 sensoren sind auch nicht teurer als ne vernünftige mechanische lda. und die paar widerstände und evtl. 2 ov's sollten preislich gar nicht ins gewicht fallen.

@joergs
yes, you are right. Mechanical LDAs are more expensive than I thought!

But I now have an idea:
One way to connect a differential pressure sensor is to connect the high-pressure side after the turbocharger and the low-pressure side in the air filter housing (after the filter). This way, you measure what the turbocharger actually needs to deliver. If the filter is not clogged, a pressure of approximately 50 mbar higher than normal will be indicated (filter pressure loss). If the filter is clogged, the pressure will be even higher, and you will notice the problem. However, you cannot use it to monitor a loading bay, but the 1Z doesn't have one anyway.

Sounds pretty good, right?