The Eagle has an I2C interface, which is used to interface to sensors. The I2C interface is a 'shared bus' protocol. So you can hook up many sensors at once. However the way we can read from multiple sensors is that each has a unique address. Addresses are in the range 0-127 (0x00 - 0x7F) Then when taking 2 measurements, the device knows - read from Sensor 0x40 and then 0x30 for example. 

Generally, if we purchase 2 identical sensors, they will have identical addresses, so we can only use 1 of these at a time. Some models might require reprogramming the module to change the address, which isn't practical. But other sensors sometimes offer simple ways to set the address. 

For example, from Supported Sensors and Inputs, a few temp sensors that are integrated are:

• Digital Matter Temperature Probe
  • This sensor can be given 1 of 2 unique addresses by connecting the green wire to either 3V3 or GND (see Falcon - Wiring in DM I2C Sensors) So we can use 2 of these at once
• Digital Matter Temp/Hum Sensor
  • This sensor has 1 fixed address, so we can only use 1 at a time
• TMP117 Temp Sensor
  • This temp sensor (comes as a chip) - can be given 1 of 4 addresses by jumping pins on the module. So we can use 4 at a time

Equally we could use all of these together, i.e. 2 x Temp Probes + 1 x Temp/Hum Sensor + 4 x TMP117. Given all 7 have unique I2C addresses. 

Other Limitations

While we can theoretically be connecting up to 128 sensors to a Eagle, we run into some other limitations that mean in practice we wouldn't really do this. 

• I2C stands for Inter-Integrated Circuit - it was designed for low speed communication between components on a circuit board. So it does not work well for long cable runs over a few metres
• Simply attaching lots of sensors is going to become impractical
• There are only 14 available analogue data fields currently on the device to store any sensor readings. So 14 is our upper limit. However if we are approaching this we should consider BLE sensor options.

The Eagle can hold data from up to 512 tags in its tag list. So theoretically, 512! Users on 3rd party platforms can easily connect up to 512 sensors, see 3rd Party Bluetooth® Tag Support, Integrating Tags and Bluetooth® Getting Started - Tags & Scanning. 

However it should be noted that for Telematics Guru users, generic tag temp data readings from the tag list data are not integrated - so generic BLE sensors we connect to the Eagle will not be able to have their temp data displayed in TG currently. For the SensorNode BLE, 2 can be used per Eagle on TG . See Connecting a SensorNode Bluetooth® to an Eagle, G120 or Remora2. 

By default, the Eagle has default settings similar to the Oyster2. To configure a sensor reading, we need to Configure a Task Schedule, to tell the Eagle to read the sensor every X minutes, and upload the readings every Y min. We may need to also apply the right parameters for specific sensors but most simply need to be selected as a task 'Item' from the dropdown. 

Sensor readings are stored in the Analogue fields (6 and 7). Most sensor types are defaulted to a certain analogue (it doesn't need to be specifically set). If we are unsure or want to find out, we can search for and add the relevant parameter tab for the sensor. What first appears is what is defaulted. We can remap the value if desired.

See Falcon Cellular - How to setup analogue sampling

No. The hardware does not support this. 
When both external power and batteries are installed, the device will use whatever is supplying the higher voltage.

This will prevent set such as installing 4 x LTC batteries (giving ~14V) in conjunction with a 5V external supply. The batteries will always be used in this configuration

When external and battery supplies are used, if there is a power cut, we swap over to batteries, and some capacity is used until external power is restored.

See Eagle and Falcon - External Voltage Disconnects

The Eagle is an extremely feature packed, configurable device. And this has implications in firmware. As a result, whenever the device needs to upload readings from a task - it will generate a log and perform a 'heartbeat' upload. This will generate an extra (redundant) log - but it cannot be disabled, and will not increase data usage in any meaningful way. 

See Eagle and Falcon - Estimating Battery Life

See Eagle: SDI-12 configuration and compatibility

The Eagle uses an internal sticker antenna with a UFL connector, which is attached to the inside of the housing and the UFL connected to the PCB.

If an external antenna is desired, the user can drill a hole in the housing, install a UFL to SMA pigtail, and then connect an external antenna.