What Is a Data Logger? Interfaces, Storage, Offline Cache, GPS, 4G and Protocol Selection

The data collector is the easiest device in the system to "buy small". Selection should not look only at the number of RS485 ports, but also consider the number of sensors, analog/digital volume, storage, communication network and future expansion.

What is a data collector

The Data Logger/Data Acquisition Unit is responsible for reading data from field devices such as RS485, RS232, 4-20mA, 0-5V, pulses or switching quantities, and completing timestamps, storage, protocol conversions, and uploads. Located between sensors and servers, it is a central device in unattended weather, agriculture, water quality and industrial IoT systems.

List all field interfaces first

• Number of RS485/RS232 ports and the planned device count on each bus.
• Number of analog inputs such as 4-20mA, 0-5V.
• Rain pulse, switching amount DI, relay DO and other interfaces.
• Whether the sensor needs to be supplied with a controlled power output.

Redetermine data strategy

The sampling period determines the amount of data and the power consumption. Minute-level meteorological data and second-level scientific research data have completely different storage requirements. The network loss scenario also confirms the local cache capacity, whether the data is cycled over, and whether the network can be retransmitted after recovery.

Networks and protocols are geared towards the final server

On-site Ethernet cable is preferred; no fixed network is available 4G; local area wireless can be combined with Wi-Fi or LoRaWAN. When going up to the self-built server, the MQTT, HTTP/ HTTPS, TCP and other protocols and data formats should be determined in advance.

GPS and remote management are not required for all projects

Fixed weather station coordinates are usually unchanged after installation and can be entered on the platform; continuous GPS is required for mobile devices. Whether remote parameter configuration, OTA and remote diagnostics are required should also be specified during the project design phase.

NiuBoL Data Acquirer Product Selection

The NiuBoL data collector product covers multiple serial ports, analog volume, switching volume, local storage and other configurations. Some RTU models offer RS485/RS232, 4-20mA/ 0-5V analog inputs, 16MB local storage and TF card expansion for meteorological, agricultural, water quality and industrial IoT systems. Product reference: NiuBoL Data Collector; Data Collector RTU.

FAQ

Q1: One RS485 port can connect many sensors, why multiple serial ports?

A1: Multiple serial ports can isolate different groups of devices, reduce the pressure of single bus polling, and also facilitate the handling of devices with different baud rates or protocols.

Q2: How long can 16MB be stored?

A2: Depends on the number of bytes per record and the sampling period. Calculations should be based on fields such as actual data frames, timestamps, device IDs, etc., not just estimates based on the number of sensors.

Q3: Is it important to disconnect from the Internet?

A3: Very important for unattended stations. When there is no local cache, a cellular network outage directly creates a data gap.

Q4: Can the collector directly control the pump or valve?

A4: Equipment with relay/ DO output and logic functions can participate in the control, but high-power pumps usually still require a contactor, inverter cabinet, or dedicated control cabinet.