Flow indicators are used in a wide variety of applications from water treatment to chemical plants to oil platforms. There are many different types of flow meters on the market including differential pressure, positive displacement, ultrasonic (spool pieces, clamp-on, insertion), turbine, magnetic (in-line, insertion, low flow), Coriolis, and vortex. It’s important to consider and compare the right features for your application. In this article, we’ll lay out the key features that are typically most critical to consider when selecting a flow indicator.
1) Accuracy
The level of accuracy you need in a meter depends on the meter’s purpose. For example, a meter measuring the flow of a chemical feed may need to be more accurate than an indicator used for general tracking of water treatment output. Any flow measurement for billing purposes, such as a water supply authority selling water to a utility, must be extremely accurate. High accuracy flow meters range from 0.1% to +/- 0.5% whereas low accuracy flow meters range from 1.0% to 3.0%.
2) Certifications
Some applications may require your indicator to have approvals such as UL, CSA, ATEX and NIST. UL and CSA certifications are required as industry standards for almost every application. ATEX is required for highly volatile applications such as mining, oil and gas. NIST states that your meter has been tested by a certified lab and it meets all the specifications listed by the manufacturer. Check with your local regulation department for clarification.
3) Environment
It is important to consider where your flow indicator is going to be mounted. NEMA 4X and IP65 certifications are important for outdoor applications where rain and washdown situations will be introduced.
You’ll also want to make sure the indicator is readable given the environmental lighting. If the indicator will be mounted in direct sunlight, you will need to look for a “positive” display with a bright background. Or if the indicator will be in a dark indoor environment, you will need a “negative” display with a dark background.
Finally, consider available housings for your flow indicator in outdoor environments. Plastic housings are lower cost, while metal and fiberglass are more expensive and last longer under extreme conditions. The most expensive housings are explosion proof, which are manufactured and certified to work in high volatile areas where gas and explosive vapers are in the air.
4) Data Monitoring & Notification
Some applications like food processing, fuels, water and wastewater, and tank farms require continuous recording of flow, while applications that involve batching of liquid amounts only require on-demand readings.
If you have a system where critical damage could occur with the incorrect flow, you should also look for an indicator with event notifications, such as high flow or zero flow alarms. Some more advanced meters with communication abilities have the option to send emails or text messages notifying a supervisor of an error conditions, such as flow dropping below a specific threshold or an overflow condition that could be detrimental to the facility.
5) Power & Communications
Flow indicators are often located remotely, so you may need to consider a battery powered device. You must also consider what output is needed to transmit data. Data is often sent to a supervisory control room or data acquisition (SCADA) system. Your flow indicator would need to have either a 4-20mA output, a communication port outputting either Modbus, Profibus, RS232/485 or an IOT protocol. Most of these signals can be retransmitted through a gateway and placed on the cloud for operators and supervisors to monitor their applications.
Flow Meters at Trumeter
At Trumeter, we have two meters that measure flow. Here’s a quick overview. of how they stack up on the features mentioned above.
Choose the APM Rate Meter for applications that use pulse inputs up to 60KHz (NPN, PNP or Push-Pull). It has a high accuracy rating of .01% for applications measuring speed, rate and flow. Certifications include CE, cUL, RoHS and UL. It works well in both indoor and outdoor environments with IP65 and NEMA 4 & 12 ratings. It can be connected to Trumeter Cloud with the APM Gateway to provide remote monitoring and alerts. And Modbus RTU is optional.
Choose the Vista Touch Flow Meter for applications that use one of 3 different types of inputs, 4-20mA, 0-10VDC or Pulse input that supports NPN or PNP, digital logic (logic 0 <0.6V; logic 1 2.5V-24V), and zero volt contact closure. It has a high accuracy rating of .1% and an industry standard 1/4 DIN housing. Certifications include CE, cUL, RoHS, UKCA and UL. It works well in both indoor and outdoor environments with IP65 and NEMA 4 & 12 ratings. It comes standard with access to Trumeter Cloud for remote monitoring and alerts. And Modbus RTU and TCP come standard.
