Nice clean prototype.
DIY Test Stand to Measure Thrust
- Thread starter jbeuckm
- Start date
Help Support The Rocketry Forum:
strud
Active Member
- Joined
- Jul 1, 2019
- Messages
- 33
- Reaction score
- 46
I have done a bit with the HX711 in the past for a high sensitivity scale but was not very impressed with the noise level.
My approach for a rocketry DAQ system was to go with a Teensy4.1 and a Texas Instruments ADS131M04 which is a simultaneous sampling, 4 differential channel 24bit ADC, running up to 32KHz.
My approach has been to buffer to ram (I have 16Mbytes) and then write to either an SD card OR USB memory stick, with files that have been fully formated with scaled data in CSV ASCII format ie so you can open them up directly in excel.
As well, it have it generating a spectrum at bespoke intervals (say 1 to 10Hz) and there is a single file with spectrum vs time generated as well in the same format.
Given that the ADC has a native input differential voltage range of +-1.2V, the 24bit resolution enables the following signal types to be directly connected ie without any amplification:
- thermocouple
- strain gauge (super low noise +-5V excitation supply included)
- mA (across precision resistor ie 20mA -> 1V)
Each channel has it's own PGA (programmable gain amplifier) so the super low voltage signals like thermocouples can be amplified a bit if needed although the 24bit resolution makes it almost unneccesary.
Prototype board below (some rework was required of the 24 -> 5V buck converter).
Example format of Raw file, real units file
And the spectrum vs time file. Values across on row 6 are frequency bins in Hz, values below are in dB
Currently working on an FTP server and a Web Server so that the unit can be remotely controlled and files pulled from the media over the ethernet (wired or wireless) link.
Triggering can be set to be by command (serial or ethernet), an individual channel threshold or a digital input. I think it will be useful to use a auto-trigger that detects the ignitor current however it might be more comforting to start by command and know the logger is running before the motor is fired.
My approach for a rocketry DAQ system was to go with a Teensy4.1 and a Texas Instruments ADS131M04 which is a simultaneous sampling, 4 differential channel 24bit ADC, running up to 32KHz.
My approach has been to buffer to ram (I have 16Mbytes) and then write to either an SD card OR USB memory stick, with files that have been fully formated with scaled data in CSV ASCII format ie so you can open them up directly in excel.
As well, it have it generating a spectrum at bespoke intervals (say 1 to 10Hz) and there is a single file with spectrum vs time generated as well in the same format.
Given that the ADC has a native input differential voltage range of +-1.2V, the 24bit resolution enables the following signal types to be directly connected ie without any amplification:
- thermocouple
- strain gauge (super low noise +-5V excitation supply included)
- mA (across precision resistor ie 20mA -> 1V)
Each channel has it's own PGA (programmable gain amplifier) so the super low voltage signals like thermocouples can be amplified a bit if needed although the 24bit resolution makes it almost unneccesary.
Prototype board below (some rework was required of the 24 -> 5V buck converter).
Example format of Raw file, real units file
And the spectrum vs time file. Values across on row 6 are frequency bins in Hz, values below are in dB
Currently working on an FTP server and a Web Server so that the unit can be remotely controlled and files pulled from the media over the ethernet (wired or wireless) link.
Triggering can be set to be by command (serial or ethernet), an individual channel threshold or a digital input. I think it will be useful to use a auto-trigger that detects the ignitor current however it might be more comforting to start by command and know the logger is running before the motor is fired.
Similar threads
