It is very difficult to find processes that are not being monitored electronically nowadays. Whether to avoid human error, to meet regulatory requirements or even to reduce costs, the vast majority of companies have already dropped outdated clipboard notes and adopted data logging and monitoring equipment. In order to help choosing the most appropriate device to each process, this article discuss the characteristics of different electronic equipment for monitoring.
In an age where everyone talks about Internet of Things, Industrial Internet of Things and Industry 4.0, it is very difficult to find processes that are not being monitored electronically. Whether to avoid human error, to meet regulatory requirements or even to reduce costs, all companies today are abandoning or have already abandoned the outdated paper notes. With the evolution of technology, it is much cheaper and safer to have equipment monitoring the process than a dedicated person to take periodic notes. Thus, it is no longer a matter of whether we should migrate process monitoring to electronic equipment, but rather which equipment / technology is most appropriate for the process. With this, in this article we will discuss the characteristics of different electronic equipment for monitoring, as well as other technologies available in the market, in order to help in choosing the most suitable for each process. We will also discuss some good practices for setting up and installing these instruments.
When we talk about data acquisition, we usually refer to equipment designed to solve a particular problem of a specific application, i.e. a process that already exists and needs to be monitored. Typical monitoring applications are:
- Counting of parts produced in a plant, to record production control;
- Water flow monitoring for monthly collection by a water utility;
- Monitoring water’s flow and pressure that supplies a city for water utility supply control;
- Temperature and pressure monitoring in different parts of the same process, for quality control;
- Temperature and humidity monitoring in product (food, medicines, sensitive products in general, etc.) storage warehouses to meet health surveillance standards;
- Among so many others.
Given the infinite applications for process monitoring around the world, it all boils down to measuring analog and / or digital quantities at a certain frequency, recording them and enabling monitoring by means of local or remote indication. Thus, in order to choose the most appropriate equipment for each process, we must describe our problem in requirements and then analyze the market options that meet them. Here are some questions to ask to help you choose the right equipment:
- Yes: give preference to devices that allow reading of multiple devices through some interface with industry standard communication protocol (such as Modbus RTU over RS485, for example);
- No: give preference to equipments that can monitor all necessary points in the process.
- Yes: choose a device that has the number of digital inputs required for my process;
• Part count: choose a device that has digital input with accumulator function and / or average count by log interval;
• Flow measurement: choose a device that can reach the maximum pulse frequency generated by the flow meter and already has functionality to calculate this type of information;
• Volume measurement: choose a device similar to the previous topic and that has totalization / accumulation functionality;
• Event Log: Choose a device that has event logging functionality and can log all events generated by the process;
• None of the above: further study the process to identify if the quantity that needs to be measured is analog or if it will be necessary to place an intermediate equipment that allows the acquisition of the desired quantity.
- No: the equipment to be chosen doesn't need a digital input.
- Yes: choose a equipment that has the number of analogl inputs required for the process;
• Temperature: choose a device with a temperature sensor input that meets the operating range, resolution and accuracy needs of the process (Thermocouple, Pt100, Pt1000, NTC, etc.);
• Humidity: choose a device that has an integrated humidity sensor or that has an accessory and meets the needs of the operating range, resolution and accuracy of the process;
• Pressure, Humidity, Temperature, Current, Voltage, Power, Lightness, etc .: There are numerous types of quantities where will be necessary to use an intermediate equipment that obtains the information and transmits it through 0-20mA / 4-20mA, 0-10V / 0-5V, 0 50mV or via any communication protocol. In these cases, it is possible to use a linear type analog input that allows you to configure the reading range according to what is being transmitted. Therefore, I should look for equipment that, together with the transmitting equipment, meets the operating range, resolution and accuracy needs of the process;
• None of the above: further study the process to identify if the quantity that needs to be measured is digital or if it will be necessary to place an intermediate equipment that allows the acquisition of the desired quantity.
- No: The chosen equipment does not need to have analog input.
In addition to checking application needs for the types of data to be monitored, you must also specify application time requirements:
• What is the input channel scan rate - with how frequency do I need to be able to read all measurement points in my process?
• What is the log rate for the read channels – with how frequency do I need to record all measurement points for future analysis of my process?
• How many records do I need to store - how long do I need to have the records saved in memory?
Just as important as being able to make the right measurement (with proper resolution and accuracy) at the right interval, is also choosing equipment with the appropriate technology. If the process requires data to be logged even in a power failure, I should look for equipment that has or fully operates with backup batteries. If data needs to be published in a supervisory or cloud system in real time, I should look for an equipment with such connectivity. If this need do not exist, I should consider how often someone will perform manually data collection, calculating the equipment to have enough memory to store the data for that period. In this case, I must also take into consideration the technology that allows me to perform more conveniently the manually data collection, such as via USB or via Bluetooth in a smartphone, for example.
Processes that require some local indication and / or alarm notification for immediate action to be taken are also common. Therefore, you must enter the requirements set whether or not you need to:
• HMI for local indication;
• Buzzer for alarm sound notification;
• SMS for alarm notification;
• email for alarm notification;
• alarm controlled by digital output;
Data loggers are electronic devices designed to periodically store analog and / or digital data, in order to enable further detailed analysis of monitored data. They are developed to meet endless applications, and new models emerge every day to make end users life easier, giving to the device more intelligence so the processes can be automated.
Generally speaking, all data loggers have one or more analog and / or digital monitoring channels, record memory and communication interface. The most complete, designed to solve the most complex applications, have multiple analog channels, multiple digital channels, some interface with industry standard communication protocol to allow reading of multiple devices, various communication protocols, some load drive outputs and allow you to program operating logic for the desired application.
In NOVUS’ Data Acquisition & Communication line, where all equipment has free software for data configuration, collection and analysis, we can find the following lines of data loggers:
Temperature loggers with integrated sensor that operate only by battery. The TagTemps are extremely compact (pocket-sized) and versatile for food and drug temperature monitoring applications, where a record interval of more than 1 minute (required to maintain battery life) is not a problem in the application. This line includes models with USB or NFC interface, for collect data through notebook or smartphone - current technologies that allow, in a simple and practical way, searching the device data without draining the battery power.
Robust, compact battery-powered data loggers for diverse applications.
LogBox RHT LCD is available to meet the needs of transportation monitoring, perishable storage, process auditing, and more. It has integrated humidity and temperature sensors with local indication on LCD display.
LogBox AA is a 2-channel universal analog input data logger for analog signal measurement compatible with a wide range of industrial signals and sensors such as Pt100, Thermocouples and linear sensors (0-50mV, 0-10V, 0-20mA or 4-20mA), allowing a wide range of applications that require monitoring up two analog quantities.
To allow applications that also require monitoring of digital quantities, such as sanitation applications, the LogBox DA has, in addition to a configurable linear analog input (0-50mV, 0-10V, 0-20mA or 4 20mA), commonly used to connect a pressure transmitter, a digital input, which can count pulses up to 4kHz, serving mainly for flow monitoring.
The LogBox Connect line is the evolution of the LogBox line, providing IoT connectivity - from device to the Cloud. In this line, every device has 1 configurable digital channel for event logging or pulse counting, for control of produced parts or flow and / or volume measurement. In addition to the digital input, all models feature up to 3 configurable universal analog inputs (Pt100, Thermocouples and linear sensors (0-50mV, 0-10V, 0-20mA or 4-20mA)), a configurable digital output for alarm triggering, local indication through an LCD display and buzzer for local alarm notification. All these input and output channels are available to suit a wide range of applications, including configuring small specific logics. Not only can all be powered by an external 10 to 30 V power supply, as each of the line's equipment stands out for its peculiarities that are intended for different applications.
LogBox BLE can be fully battery operated, being the perfect mobility solution as it allow the data to be collected not only by notebook via USB interface but also by smartphone (Android or iOS) via BLE (Bluetooth Low Energy) interface. In addition to providing mobility and fast data analysis, the smartphone Apps allow the equipment to communicate with cloud systems, making possible the analysis to be done via distributed systems.
With a concept more integrated with systems, LogBox Wi-Fi has several communication protocols implemented in its Wi-Fi interface. With LogBox Wi-Fi is easy to automatically integrate the process with cloud systems such as NOVUS Cloud and AWS, as well as MQTT protocol systems or legacy Modbus TCP protocol systems. The device also allows alarms notification via email. Thus, with LogBox Wi-Fi, simply integrate it with the desired system using the local Wi-Fi network infrastructure so you do not have to manually collect data monitored by the device. Although the equipment requires external power to connect to Wi-Fi networks, the device has backup batteries that will provide enough power for more than a year to monitor the process even in the event of power outages, publishing the retained data from memory as soon as power and connection to the system are restored.
LogBox 3G is entirely based on cloud systems, with direct connection to NOVUS Cloud, where the device can be accessed for configuration and / or data collection localy (via USB) or remotely (via NOVUS Cloud). It's the perfect device for distributed applications where you need to monitor remote processes without Wi-Fi connectivity. Simply insert a SIM CARD with a data plan enabled, make the power and sensor connections on the device, and register it on NOVUS Cloud through NXperience software to access data from anywhere in the world. It has also an alternative model with GPS geolocation, contributing to applications that need to monitor the location of the merchandise. In order to the process never stops being monitored, in the event of a power outage, it keeps scanning the sensors and publishing into the CLOUD for a few hours through internal batteries that automatically recharge when power is restored.
Fieldlogger is the most versatile data logger in NOVUS line and is often used in place of PLCs for monitoring and performing small tasks. Its 8 universal analog input channels, 8 configurable digital input / output channels, two relays and RS485 interface for reading up to 64 remote Modbus RTU devices allow you to monitor a multitude of processes.
In addition, FieldLogger has SD card memory expansion slot, allowing to record up to 16 GB of data; USB OTG interface for data collection via USB stick; graphic display for local visualization of the process; and Ethernet interface for remote process management through numerous protocols, having various functionalities through Modbus TCP, HTTP, FTP, SMTP, SNMP, etc. protocols.
Due to all these characteristics, it is the perfect equipment for monitoring large processes that need to register a large number of points, both analog and digital, being near or far from the equipment, where, in the latter case, it is possible to use auxiliarie equipments that communicate as slaves from a Mobdus RTU network. In addition, due to the numerous alarm configurations and digital outputs available on the equipment, it is possible to implement small control logic for the application.
After study the process to be monitored, survey the requirements and knowing the available commercially dataloggers, it is possible to choose the most suitable one to solve the application. Now, simply choosing the right sensors and transmitters will measure the analog and digital variables and perform the set up.
• Read the user manual carefully, it may contain important tips for the process and prevent installation failures;
• Electronic and analog signal conductors should be routed separately from the output and power conductors, if possible on grounded conduits;
• The energy power to the instruments must come from an instrumentation network;
• It is recommended to use RC FILTERS (noise suppressor) in contactor coils, solenoids, etc.;
• In control applications, it is essential to consider what can happen when any part of the system fails. The internal devices of the equipment do not guarantee total protection;
• When choosing temperature sensors, look for the type that provides the best resolution in the process measurement range;
• When using Pt100 or Pt1000 type sensors, give preference to using 3 or 4 wire sensors, thus, in addition to allowing the equipment to indicate sensor failure, it also allows it to calculate and compensate for cable resistance, which, if not compensated, it may represent some °F error in sensor reading.
• When using thermocouple sensors, be sure to use the correct compensation cable from the sensor to the measuring equipment. For these types of sensors, the equipment has an internal temperature sensor (called cold junction) that is used to compensate the temperature at the junction between the thermocouple element and the equipment connection terminal. If the correct compensation cable is not used, the temperature difference between the sensor element and the equipment will appear as a reading error in °F.
• Sensing elements have a very weak signal, are susceptible to electromagnetic noise and may produce reading oscillation. Therefore, if any measurement point is too far from the datalogger, use a 4-20mA or 0-10V transmitter to transmit the signal to the datalogger.
In devices with more than one input channel, ground is usually common to them, ie the negative ("-") terminals of the channels are internally interconnected. Therefore, when measuring current signals (typically signals from transmitters), care must be taken in the connection so that there is no interference between them.
The correct way to connect is always to leave the measuring instrument (with common ground) "last" in the current path, that is, with the input negatives directly connected to the power supply negative. This prevents interference from the different currents in the input channels.
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