Bocsh Sensor Wiring

Jimster
Posts: 134
Joined: Wed Mar 19, 2008 11:06 pm
Location: Bridgend, South Wales
Contact:

Bocsh Sensor Wiring

Postby Jimster » Wed Apr 02, 2008 6:35 pm

Hello,

Please can you give me some advice to give me some more confidence before I blow things up.
ok I’m just about to start connecting my DL1 and Dash2, but before I get the soldering iron out, I just want to check I’m doing everything correct.

I’m thinking of making the below circuit
(Each resistor would be 1k.)
Image
Can you see any problems in this?

Also would I be able to log values from the DA channels in the DL1?

If I am sharing a sensor with my ECU (TPS & MAP) I assume I simply ‘T’ in to the variable voltage side of the sensor, and connect to one of the inputs? I assume I don’t need to use a 1k resistor with these too?

any advice / comments would be great,

Cheers

Jim

faraday
Posts: 267
Joined: Sun Feb 25, 2007 1:18 am

Postby faraday » Thu Apr 03, 2008 1:42 am

log values from the DA channels in the DL1


What do you mean by values and DA?

In your circuits, you are making a votage divider, so the logger input value will depend on the added (fixed 1k) resistance. I assume that R-T's advice when connecting two wire sensors is precisely what you are proposing, so any calibration equation that they provide (assuming you're talking about precisely same specific sensor) should be adequate.

However, when is a 1k resistor 1k?
=> use high tolerance

Recent posts have tabulated various R vs Temp or Press. Have a search for the sensors you've found, or for peace of mind, grab a thermometer and do your own calibration. Three or four well spaced points will get you pretty close.

I assume the OHM's law mathematics is within your grasp. If not, please don't be too embarrased to say so.
Write down the equations for a few resistance values. If the sensor has appropriate sensitivity, the 1k + or - values will probably be insignificant.

I don't think your proposal will blow anything up. More risk that you'll burn an inquisitive cat that might wonder what you're up to!
Wire up your sensors and resistors to the logger and use "Monitor" to view the voltages as you do the calibration. This way, the values of the resistor and variation in the sensor is compensated for in your specific calibration.
The accuracy will depend on your thermometer and technique. There is variation in everything. No measurement is black and white absolutely accurate.
By doing your own calibration you will learn what confidence to place on the data you eventually log.

Apologies if my suggestions come across as pedantic platitudes.

The logger's AV inputs are measuring a voltage and (should) scarcely affect the current in the circuit. But to what voltage is the sensed voltage referenced?
If there's an existing sensor being given an upper reference voltage from another device, then a common ground is an appropriate reference, but I suppose you have to be aware of ground loops.
The upper reference voltage, wether from the R-T device's 5V or another device, is regulated and can only supply low currents, so it will not blow anything up, but is there sufficient capacity to drive the circuit you've hooked it up to?

At this stage, I am getting out of my depth. I am mechanical, not electrical. If I'm offering bad advice, I hope someone out there will offer corrections.

It would be nice if the R-T documentation included some wiring diagrams. Most other brands of data loggers do, but most other brands are more expensive.

You're obviously keen to collect a decent quantity of data and want it to be quality data as well. The economy of the R-T kit will not prevent this. It is very good value.
Ultimately you may run out of R-T inputs. Taking the engine data as a serial stream from the ECU to the R-T serial input has advantages.
Is this possible with your gear?

Best Wishes :)

Jimster
Posts: 134
Joined: Wed Mar 19, 2008 11:06 pm
Location: Bridgend, South Wales
Contact:

Postby Jimster » Thu Apr 03, 2008 7:43 am

faraday wrote:
log values from the DA channels in the DL1


What do you mean by values and DA?


by DA I refer to the channels on my Dash2,

thanks for all your advice.

Cheers

Jim

faraday
Posts: 267
Joined: Sun Feb 25, 2007 1:18 am

Postby faraday » Thu Apr 03, 2008 3:42 pm

No probs then?

Hope you're cookin' with gas. 8)

stevieturbo
Posts: 55
Joined: Sat Jul 05, 2008 3:54 pm
Location: Northern Ireland

Postby stevieturbo » Sat Jul 05, 2008 4:14 pm

Out of interest...what Bosch air temp sensor are you using ??

I had been using the small plastic tipped one until a week or so ago. It was soooo slow to react, 20s response time !!!!

Ive a proper thermistor type in now, and temps Im seeing are so different now !!!!
I had no idea they were so far off with the slow sensor.

Jimster
Posts: 134
Joined: Wed Mar 19, 2008 11:06 pm
Location: Bridgend, South Wales
Contact:

Postby Jimster » Mon Jul 07, 2008 9:45 am

Hi Stevie, I'm using the thermistor type, I've always used them and find the responce very fast


Return to “Sensor-related questions”

Who is online

Users browsing this forum: No registered users and 22 guests