Multiple tariff and time-of-use data capabilities are just some of the complex demands being made on designers of electronic meter systems worldwide, particularly as the need for more sophisticated utility distribution management systems grow. Ramtron International Corporation is providing a solution to these difficult data collection needs with FRAM (ferroelectric random access memory) products.
FRAM nonvolatile memory offers an optimised, easy-to-use solution for a variety of advanced electronic metering systems, whether metering electricity, water, gas or heat. In the first half of 2002, Ramtron shipped more than 5 million FRAM memory devices into metering products worldwide.
FRAM memories offer three distinct benefits to electric meter manufacturers. First, FRAM is capable of collecting data for an unlimited period without wearing out. Writing to FRAM memory once per second for 20 years won't even begin to impact on its performance. FRAM memory has the ability to record power usage over time, allowing variable pricing schemes that could play a major role in smoothing peak power demand for efficient power management systems.
In an electricity meter, for instance, FRAM can be written every minute – or second – for the life of a meter, allowing time-of-use to be logged along with power consumption. Less advanced digital meters must only write data when power is failing, because other memory products wear out quickly if they are written too often. Ramtron International offers FRAM products in virtually any size needed for today's electronic meter applications. Low cost residential meters use 4-kilobit or 16-kilobit memories, but the trend is toward higher densities in larger meter installations.
In addition to high endurance, FRAM products operate with very low power consumption. These devices run from under 1 micro amp standby, and use only 100 micro amps or less when being accessed. Large installations must minimise watt stealing by meters, and FRAM memories offer the lowest impact on energy usage of any memory technology. In addition, Ramtron's new line of 3V operation solutions is ideal for battery-powered applications like water meters. In a water meter, FRAM uses substantially less battery life than previously-favoured memory solutions. Therefore FRAM is desirable in utility meters even when data is not being permanently stored in the memory.
The third benefit of Ramtron's FRAM memories is speed. The device is ideal for electronic meters that must continually read and capture data. FRAM captures power use data with exceptional speed, which can be a significant advantage when there is a power outage. If power goes out, a typical meter may not be able to record the last reading of usage. When a power outage is widespread, the loss of billing data may be financially significant for the utility provider. FRAM access speed is so fast that it is virtually impossible to lose even one second's worth of power usage.
Ramtron's nonvolatile FRAM technology is ideal for metering activity that requires frequent, fast, or low power writing of data, and is becoming the preferred memory solution in electronic meters around the world.
Italian AMR project chooses FRAM
In August 2001 Ramtron and UK-based Ampy Automation Digilog Limited signed an agreement that called for the purchase of Ramtron's FRAM memory products for use in a sophisticated electronic meter programme that is now the world's largest digital meter installation. The Enel utility's AMR programme calls for 27 million homes in Italy to receive new meters that use FRAM technology over the next three years. Andy Robinson, design manager for Ampy, commented, “Utility meter products have a long life and must perform virtually maintenance-free while providing highly-reliable usage data. In the past, it has been difficult to meet all data collection criteria. We have been limited by memory write speed and by the relatively low number of times that the memory could be reliably written. FRAM solves these problems, with margin to spare.” The Enel installation is now underway, with millions of meters having been built with FRAM technology.
Pre-pay scheme in South Africa using FRAM
Schlumberger is another meter manufacturer that benefits from FRAM, having used FRAM in their Eskom meter, a low-cost prepayment electricity meter for South Africa. Schlumberger is one of the key meter suppliers in South Africa, another country currently under-going rapid electrification. In this case, the meter is based on a pre-paid scheme where the home user must pay for electricity in advance. FRAM is used as non-volatile data storage for the meter's identity and operational data, as well as the customer's power credit balance.
“FRAM was chosen by Schlumberger for its ability to write data at full speed, avoiding the complexity of a write-back pipeline to be managed at power down, and for its write cycle endurance, which allows data to be written at frequent intervals,” says Malcolm Rowe of Schlumberger. “In our case, we write data such as customer's outstanding credit back at 2 second intervals over the 10-year life of the product.”
China values the FRAM advantage
Six of China's largest utility meter manufacturers have selected FRAM for use in a variety of single- and triple-phase multi-rate digital power meters. These manufacturers have chosen Ramtron's nonvolatile FRAM memory for its high-reliability features, including superior write endurance, fast read/write speed and low power operation. China is expected to rapidly adopt electronic meters digital time-of-use, and FRAM is emerging as the memory solution of choice for meter development programmes totalling multiple millions of units per year. Among the companies designing FRAM into their metering products are Hangzhou Holley Group, Jiangsu Linyang Electronics, Hunan Weisheng Electronics, Shenzhen Longdian, Hangzhou Hualong Electronics and Henan Star Instrument.