MCC 134 gives my negative temp back without any sensor connected

[bbfjumper]

Hi,

 

as I mentioned in the title i want to read out temperature values and stream it via serial port. The Problem is, that i get for every sensor port, without having a sensor connected, a strange negative value (-127.3...)

 

My code for reading out the sensors is:

import time
from sys import stdout

import serial
import serial.tools.list_ports
from daqhats import HatError, HatIDs, TcTypes, mcc134

from lib.daqhats_utils import select_hat_device

# Constants
CURSOR_BACK_2 = "\x1b[2D"
ERASE_TO_END_OF_LINE = "\x1b[0K"


def read_temp():
    """
    Reads temperature values from multiple channels of an MCC 134 hat device.

    Returns:
        list: A list of temperature values read from each channel.

    Raises:
        HatError: If there is an error with the hat device.
        ValueError: If there is an invalid value.

    """
    # Rest of the code...
    tc_type = TcTypes.TYPE_K  # change this to the desired thermocouple type
    channels = (0, 1, 2, 3)

    try:
        # Get an instance of the selected hat device object.
        address = select_hat_device(HatIDs.MCC_134)
        hat = mcc134(address)

        for channel in channels:
            hat.tc_type_write(channel, tc_type)

        try:
            temp_values = []
            for channel in channels:
                temp_values.append(hat.t_in_read(channel))

            stdout.flush()
            return temp_values

        except KeyboardInterrupt:
            # Clear the '^C' from the display.
            print(CURSOR_BACK_2, ERASE_TO_END_OF_LINE, "\n")

    except (HatError, ValueError) as error:
        print("\n", error)


def find_serial_port() -> serial.Serial:
    """Find the first available serial port."""
    ports = serial.tools.list_ports.comports()  
    for port in ports:
        if port.description != "n/a":
            return port.device
    raise Exception("No valid serial port found")


def send_floats(floats: list[float]) -> None:
    """Send a list of floats over the specified serial port."""
    # "/dev/ttyAMA0" is the default serial port on Raspberry Pi
    with serial.Serial("/dev/ttyAMA0", 9600, timeout=1) as ser:
        for f in floats:
            ser.write(f"{f:.2f};".encode())
            print(f"sent: {f}")
        ser.write(b"\n")


if __name__ == "__main__":
    try:
        while True:
            send_floats(read_temp())
            time.sleep(2)
    except KeyboardInterrupt:
        print("\nExiting...")

Would be great if someone could help me or maybe have/had the same issue.

 

BR

[Fausto]

Hello @bbfjumper.

Data acquired by a MCC 134 on an open channel is not valid.  A thermocouple wire should be connected to the desired channel terminals when attempting an acquisition.

Regards,

Fausto

[bbfjumper]

Hi Fausto,

 

thanks for the quick reply. It makes no difference even if i connect a sensor or not...

 

[Fausto]

Hello @bbfjumper.

Please connect a thermocouple wire to the analog input terminals (CH#H and CH#L). Use the MCC DAQ HAT Manager to read the thermocouple channel.  What is the reading?  Test each channel option with a thermocouple via the MCC DAQ HAT Manager's channel selection for the MCC 134. Do any of the available channel selections in the application read the correct temperature?

Regards,

Fausto