The Outpost EVO2, WASP2 and COBRA2 products can have 1 or more 4-20mA channels depending on product code.
The 4-20mA channel inputs are designed to read from loop-powered 4-20mA sensors that are powered either from the switched power output source of the Outpost itself or from an external permanent power source.
The 4-20mA inputs on an Outpost are generally intended to read sensors that are both powered and read from the Outpost, therefore the 4-20mA device itself is powered from the Outpost power source (generally a battery or solar panel).
This creates a stand-alone system fully battery powered and isolated from other noise sources and from ground. Telemetry communications are entirely wireless through the Outposts cellular modem, and setup is performed entirely through the mobile install app or website.
The 4-20mA analogue connectors typically come with 3 cables - see 4-20mA Connector for more details.
General Characteristics of the Outpost 4-20mA channel:
- Single-ended (must form the last device in a 4-20mA loop if there are more than one device reading the sensor output)
- 200 ohm input impedance (takes 4V from the loop)
- 16-bit resolution, with 1% accuracy
- SPO fixed at 12V (For more detail see Output Power)
- Tolerant to 9V permanent over-voltage applied to the 4-20mA channels
Diagram of 4-20mA loop powered setup:
For more connection options see Logger connect 4-20 mA.pdf
To ensure the attached 4-20mA sensor is compatible with the Outpost, the SPO stabilization time must be set to ensure the sensor device has enough time to power up and stabilize it's output before it is sampled. The sensor device will then powered-down again.
The stabilization time for each 4-20mA channel is programmed through the website interface. See Calibrating 4-20mA Analogue Channel for more info.