Thank you for your observations with regard to the ADC-24. Further to your inquiry with regard to the 2ma of current provided as an additional feature of the ADC 24.
The ADC-24 has been designed with the following in mind. The ADC-20 and ADC-24 High-Resolution Data Loggers offer the ultimate in precise and accurate readings. Features such as true differential inputs, galvanic isolation and software-selectable sample rates all contribute to a superior noise-free resolution.
The ADC-20 is equipped with a 20-bit A/D converter, and can maintain a gain error of 0.2%. The four true differential inputs may be configured as eight single-ended inputs or any combination in between, such as two differential and four single-ended. The ADC-24 is equipped with a 24-bit A/D converter, and can maintain a gain error of 0.1%. The eight true differential inputs may be configured as 16 single-ended inputs or any combination in between. Power and connection to a PC or laptop is through a USB 1.1 or USB 2.0 port. Using the supplied PicoLog software, you can record,
monitor and analyse collected data.
In essence you would need an independent power supply. This would be the preferred methodology and you will not be able to increase the current giving capacity as the logger was never designed to accommodate the functionality of being a power supply for multiple sensors.
It would be better to use a dedicated power supply in this instance.
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Also I wish you a very merry Christmas,