Hi all, I am using Edwards TruWave Pressure Sensor to measure pressure. The specific device is Edwards Lifescience PX6001 “TruWave pressure monitoring set”. The design project focuses on measuring pressure changes through tubular vessels. I am having trouble connecting the TruWave Pressure Sensor (image below) to the Arduino since it has five connectors instead of the typical three in many pressure sensors. Any help would be appreciated.
Link to specifications I could find:
There is not an data on the interface in that PDF.
You need to know what each of the electrical connections are and what they do. Also the mechanical interface as well, i.e. what connector the sensor mates to.
You will probaly have to go back to the supplier or manufacturers for this.
I would cut the connector off and see how many wires there are. Then take resistance measurements between pairs of wires.
The brochure says "Sensitivity 5.0μ V/V/mm Hg ± 1%". The Arduino analog inputs aren't good in the microvolt region so you will need an amplifier or a more sensitive A/D converter. Maybe the HX711 Load Cell Amplifier would work.
I contacted the supplier/manufacturer and was told it was proprietary information.
Just purchased! I'll let you know how it goes. Thanks
Adding to what John Wassser commented above. I would guess the pressure transducer is a strain gauge type bridge, with four connections; excitation and a return plus two sensing on the bridge. The fifth connection could be a screen for the cable.
For this application, does the HX711 require a simple analog read or would it require the HX711 library to read a voltage signal?
I think the HX711 is a Wire/TWI/I2C device.
I forgot to post, but your advice and suggestion worked like a charm! I appreciate your advice and wisdom!! 
It has clock and a data pins, but it's not Wire/I2C.
No, it has a digital output, but sometimes you see them connected to the analogue pins.
The analogue pins are then used as digital inputs.
A HX711 library can do all the heavy lifting for you.
Note that a common HX711 board is 5volt logic only.
If you are going to use a 3.3volt processor, then you need the Sparkfun version of the board.
Leo..
Thank you! Is it possible to increase the sample rate through progamming/code only? I know that the sample rate can be increased by altering the HX711 pins.
No, sampling takes time.
Should be 100ms or there abouts on the default 10Hz setting.
How much is it...
Leo..
Currently, it is at the default with 10 Hz. I want to increase the number of data points taken. The current sample rate does not take enough points to develop a plot with pressure values (see the image below). It would be nice to have an increased number of values that would be between 100 to 45 to approximately 0.
Note: The equation to turn ADC readings into pressure was developed using a manometer/pressure gauge and linear calibration (incase someone in the future wanted to reference this project/post)
What is the serial monitor set to. If set to 9600, then the blocks you're printing (~100ms) take about the same time as the HX711 measuring interval.
The only way to speed up the HX711 is a hardware change.
You loose accuracy because of added noise and no mains hum averaging.
Leo..
The serial monitor is currently set to 115200. I'll change the hardware to increase the sample rate. Thank you for the help!
One last question, could you point me in a good direction to develop pressure versus time plots for the sensor based on the HX711? I have some ideas based on youtube videos, but was wondering if you had anything you would recommend?
Time since start, or exact time.
Could use millis() for the first and a RTC or NTP for the second option.
Just save the raw data from the HX711, and convert to pressure before printing/plotting.
Save where. SD card?
Leo..
@UneducatedBlockhead Can you share what you found for the pinout on the edwards transducer? which pins on the HX711 did you connect to which wires on the edwards transducer?
You can check out US patent US7604602B2 for the pinout and a functional description about the RC sense/identification mechanism that is built into the cable and transducer itself.
Especially the following picture that can be found in the patent is pretty self-explanatory:
https://patentimages.storage.googleapis.com/1a/d2/d3/a7fb5297875242/US07604602-20091020-D00000.png
Yes, sorry forgot to reply (I thought I replied already). The pin connections in the patent are correct. For connecting to the HX711, use the following pins:
Wire EX: Transducer |HX711
Wire 1: V+ (5V) |E+
Wire 2: SIGNAL+ | A+
Wire 3: SIGNAL- | A-
Wire 4: V- (GND) |E-
If you are curious, how I solved this without the patent, I found a pair of resistance measurements between pairs of wires.
