Syncronising Bluetooth transmitter with sampling

Question

I make a data ackusiton system that samples data from some sensors. Sampling speed is in the range of 100-10 kHz. On the board there is a Bluetooth module that transmitts data.

The problem is that if the range is long, more than a few meters, the noise from the module increases to unaccaptable levels. To avoid this there are filters between analogue, digital and radio parts but it was not enough if the module is increasing the power.

One way to totally avoid the noise would be to avoid sampling when the transmitter is working. Transmission is done in very small pulses so it would not interfere so much with the sampling even that it will result in a slightly varying sampling positions. I figure to check the power supply at the module to detect transmission but maybe there are som better method. Suggestions?

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magnet · Answer

If you are getting signals from the transmitter into your sensor inputs you need to filter/bypass the inputs. Bluetooth transmitters are spread spectrum 2.4 GHz, so their output by definition resembles noise in their transmission bandwidth. Or you may need to shield the analog sections (unlikely it is getting in through the digital sections). Could the problem be inadequate decoupling on the power supply rails? This assumes everything is running off of the same supply. Are the sensors prone to RF interference? The vendor may be able to suggest how to handle this. Your sample rate suggests a relatively slow changing input so either an LC filter or ferrites may be necessary.