MAX31855KASA+T: FAQ

Can I drive the MAX31855 SPI pins with a 5V supply?

No, the MAX31855’s SPI interface must not have voltage higher than 4.0V applied. High voltage and high current (through a voltage-divider) will induce self-heat resulting in cold-junction and thermocouple…

Does the MAX31855 have any filtering for EMI or RF frequencies?

No. The MAX31855 does not have any on-board 50/60Hz notch filtering, nor does it have any high frequency filters. A 10nF ceramic capacitor (maximum value) should be placed as close to theMAX31855 package…

Does the MAX31855 linearize the thermocouple result?

No. While the MAX31855 does perform automatic cold-junction compensation, it does not perform any linearization calculations. Linearizing the thermocouple results needs to be performed externally using…

I am experiencing temperature errors due to noise induced on the thermocouple cable. Can I connect the T- terminal to the GND of the MAX31855 to help eliminate that error?

Yes, but you will lose some fault detection capability since you are intentionally grounding the T- portion of the cable, and you may experience a slight decrease in thermocouple temperature accuracy since…

Is the SDO (data out) pin of MAX31855 tri-stated ?

Yes, when /CS is inactive high, the SDO (data out) pin is high-impedance (tri-stated). The MAX31855 will not drive a signal on the SDO pin when the chip select pin is inactive, and thus will not load the…

MAX31855TASA 测量负温度问题误差很大，如何解决？

在使用MAX31855T + T型热电偶测量温度的时候发现测量严重偏差，问题如下： 1. 正温度，常温下偏差还算正常，误差约在±1℃左右。高温区偏差较大，热电偶放到沸水里面实测读数80.3℃，误差约20℃； 2. 负温度偏差大（这个温区也是我的产品主要使用场景），实际-32℃，读数只有-14℃；实际-14℃，读数只有-5℃左右；排查措施： 1. 使用热电偶校验仪表做了校验…

To realize multi-channel thermocouple temperature measurement with multiple MAX31855 chips, can the T- of multiple MAX31855's be connected together?

No, it is necessary to ensure that each MAX31855 is independently measuring the corresponding channel's thermocouple, with each thermocouple being independent. The T- cannot be connected. During the conversion…

Using MAX31855KASA, the result read(0x7D5023D0) indicates that there are no malfunctions. However, the thermocouple temperature is 2005 degree C, and the reference junction temperature is 35.81 degree C, which is incorrect.

There are two possible causes of this problem: 1. SPI communication error. If the reference junction temperature is confirmed to be at 35 degree, the reference junction reading is correct. If the temperature…

What could cause large errors between a generated signal and measured values for a thermocouple when interfacing to the MAX31855K?

When using a signal generator or thermocouple simulator, it is recommended to connect directly to the T+ and T- of the MAX31855K. Long cable connections to the T+ and T- terminals of the MAX31855K may…

What is the temperature conversion behavior of the MAX31855 if the thermocouple leads are connected in reverse?

When a thermocouple's leads are connected in reverse to the MAX31855 T+/T- pins, you will see the reported value of thermocouple temperature decrease as the actual temperature at the thermocouple tip increases…

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