Hi Sir,
We are using ADS1291 to design a ECG&PPG product, and using the lead-off detection function of it. But it doesn't work normally. The problem description is as follows:
1. In an environment with high interference, the electrode contact status can be read in the LOFF_STAT register. But in an environment with low interference, the electrode status read in the LOFF_STAT register is non-contact (IN1N_OFF and IN1P_OFF bits are always zero). We are trying to adjust the voltage comparator COMP_TH[2:0] but the problem is still exist.
2. Read the LOFF_STAT register in an environment with high interference. When COMP_TH[2:0] is set to a maximum of 95%, it can effectively identify the contact state of a single electrode, but the IN1N_OFF and IN1P_OF bits will both be zero when two electrodes are in contact at the same time.
When the COMP_TH[2:0] is set to a minimum of 70%, the IN1N_OFF and IN1P_OF bits will both be 1 with two electrodes are in contact at the same time, but when a single electrode is in contact, the value of IN1N_OFF and IN1P_OF bits is uncertain.
The schematic diagram is as follows:
The parameter setting on the software is as follows:
CONFIG2: Configuration Register 2 (address = 02h): 0xE0
PDB_LOFF_COMP=1
LOFF: Lead-Off Control Register(address = 03h): 0x10
COMP_TH[2:0]=000
ILEAD_OFF[1:0]=00
FLEAD_OFF=0
LOFF_SENS: Lead-Off Sense Selection (address = 07h): 0x03
LOFF1N=1
LOFF1P=1
So does it possible to determine that the detection electrode is in contact with the human body without an external detection circuit? How to configure the software at this time?
Thanks,
Best Regards
