Echoes and Challenges of Technological Limitations

How did engineers in the past manage to measure electrical power without modern microchips and DSPs? This article explores theEnergomera CE6806P, a device created in 2006 for verifying electricity meters, yet built using 1980s-era technology.

We’ll take a closer look at its design, principles of operation, and howdiscrete-analog solutionswere used to achieve high accuracy. The Energomera is a fascinating example of engineering and ingenuity, giving us a unique perspective on theevolution of electrical measurement devices.

Modern Energy Metering Technologies

Today, measuring electrical energy is a straightforward task, thanks to specialized metering chips. This is the same approach we use in ourWB-MAP devices, which rely on Microchip’sATM90E32AS andATM90E36A. There are also many other manufacturers of metering ICs, including Western, Chinese, Russian, and even South African companies.

Nearly all of these chips operate in a similar way.Voltage signals(from a calibrated voltage divider) and current signals(from a current transformer or shunt) arefedinto 24-bit sigma-delta ADCs with a very high dynamicrange. The sampled values are then processed by a dedicateddigital signal processor (DSP).

Typically, the DSP:

• Downsamples voltage and current readings to 2 kHz

• Multiplies these values to obtain instantaneous power every 0.5 ms

• Integrates the results to determine active power consumption

Additionally, the DSP calculates other useful parameters:

• Network frequency

• RMS voltage and current

• Reactive power

• Phase angles

But these microchips have only been in widespread use for about 30 years. Sohow was this done before?

Let’s Dive into History

In the earliest DC power networks, engineers even used electrochemical meters that worked by transferringmercurybetweentwo electrodes throughelectrolysis. Incredibly, similar devices were still used in Soviet measuring instruments to track operational time until the 1980s.

Here’s how they worked:

• The voltagecoil induces eddy currents in the disk, interacting with the field of the current coil to create a rotational force.

• The current coil does the same, producing its ownrotational force.

• These forces sum together, resulting in a rotation proportional toinstantaneous power.

• A magnetic brake slows the disk, balancing the force.

• Rotation is transferred via aworm gearto a mechanical drum counter, which accumulates and displays total energyconsumption.

Amazingly, despite being over a century old, this mechanism performs the exact same power calculations as modern metering chips. The disk’s speed is directly proportional to active power consumption, even accounting for phase angles and waveform distortions. The drum counter is simply a mechanical integrator that accumulates energy over time.

In three-phase meters, this system is duplicated two or three times, with additional aluminum disks. The rotational moments are summed, just like in modern three-phase power calculations.

And just look at the insane number of washers, wires, and tiny screws used for calibration — all adjusted by hand! Can you really compare this to an electronic meter, which an automated system calibrates in minutes?

Transitioning to Electronic Power Calculations

By the 1970s-1990s, engineersattempted to perform powercalculationselectronically, but high-resolutionADCs and DSPs were stillunavailable. Instead, they used hybrid discrete-analog methods, combining:

• CMOS 4000-series logic

• Analog MOS switches

• Operational amplifiers

Recently, we got our hands on aninteresting relic. Although manufactured in 2006, its technology harkens back to the 1980s. Unlike standard energy meters, the Energomera CE6806P wasn’t designed for metering but for verifying and calibrating electricity meters. As such, it was meant to have higher accuracy—though, after analyzing its construction, we’re not so sure about that! 😊

Energomera

Energomera is one of the largest post-Soviet manufacturers of electricity meters, producing both household and industrial solutions. While best known for its mass-produced utility meters, the CE6806P belongs to a different category — a specialized calibration tool rooted in 1980s engineering.

Wiren Board specializes in industrial, facility, and home automation, designing modular, Linux-powered controllers for diverse monitoring and control applications. With production facilities in Astana and Yerevan, we serve both home appliance solutions and industrial automation needs. For us the Energomera CE6806P reflects a key transition in metering technology — bridging analog precision with early digital logic — an evolution that aligns with our commitment to advancing automation solutions.

Energomera, the company behind this device, is one of the largest post-soviet manufacturers of electricity meters, producing both household and industrial energy metering solutions. Since the 1990s, it has developed a wide range of devices, from mechanical induction meters to modern digital smart meters with automated data collection. While the company is best known for its mass-produced utility meters, the CE6806P represents a different category—a specialized calibration tool designed to test and verify other meters. And unlike the company’s mainstream products, this device carries the distinct flavor of 1980s engineering. 

As an automationhardware designer andmanufacturer with production facilities in Astana and Yerevan, we atWiren Board feel both a historical connection to this device and a deep engineering curiosity about its design. The CE6806P embodies a transitional era in metering technology, blendinganalog precision with earlydigital logic — a fascinating approach that resonates with our own interest in the evolution of industrial automation. Let’s take a closer look at how it works.

Design of the Energomera CE6806P

Housed in a rugged plastic case (similar to a Peli Case), the front panel features:

• Terminals for voltage and current channel connections

• Clamp meter ports for external current transformers

• A specialized sensor for detecting the rotation of a meter’s disk

Keycomponentsinclude:

• Microcontroller board (top-right)

• Current channel amplifiers (top-left)

• Rotary switches for voltage and current channel settings

• LCD display module (center)

• Power transformer and protection components (bottom section)

Here we see three high-quality voltage transformers—no expense was spared on materials. This is necessary to ensure minimal voltage loss due to winding resistance and, consequently, high accuracy. We can also spot three current transformers hidden under the terminal blocks, along with the calculator board itself.

Computing Board: A Mix of Technologies from the Perestroika Era

ThePerestroikaera was a time of transition, where the Soviet electronics industry, once isolated and reliant on domestic components, began integrating imported technologies amid economic and supply chain disruptions. This led to a peculiar mix ofold Soviet engineering traditions with newly accessiblemodern components, creating devices that combined legacy circuit design with whatever parts were available. The result was often an eclectic blend of cutting-edge ideas and outdated manufacturing constraints, as engineers adapted to a rapidly changing technological landscape. The computing board in this device is a true Perestroika-eramix of components. It includes both branded modern microchips from TI, Philips, and Onsemi, as well as the good old Soviet K561LN2 logic chips.

The core of the board is 4000-series CMOS logic, complemented by:

• OP07 operational amplifiers — old but fairly precise,

• LM211 comparators,

• Soviet JFET operational amplifiers K544UD1,

• Hybrid SES4 microcircuits — laser-trimmed resistor arrays forming a 6-bit R-2R ladder network.

Hybrid microchips with the unusual nameSES4 are laser-trimmed resistor arrays in the form of a6-bit R-2R matrix. In the Russian internet, you can find photos of these chips with their casings removed.

Typically, R-2R matrices are associated with DACs, but here they serve asprecise fixed dividers in reference voltage circuits. Unfortunately, the capacitors used in this design arestandard Soviet polyester K73-17, which have never been known for outstanding quality. Surprisingly, they are even used inprecision circuits. For calibration, the device includes a large number ofmulti-turn trimmer resistors.

Processor Board

At the heart of the board is anAT89C52 microcontroller, a classic Atmel chip from the enhanced Intel 8051 family — the dominant architecturebefore the rise ofAVR (Arduino, etc.).

One can only wonder how much life is left in the electrolyticcapacitors from 2006.

Display Board

The designers resistedthe trend of the time to usecharacter LCD displays with a Hitachi controller and parallel interface. Instead, they went their own way, opting for apassive 7-segment LCD display.

Typically, such displays require a dedicated driver chip with exclusive OR gates on the outputs, designed to generate AC signals for LCD operation. But here, instead of a standard solution, they built acustom driver using six cascaded MC14094 chips — an 8-bit shift register, essentially an older cousin of the now-popular 74HC595.

A critical point: LCDs must be driven by AC signals withbalanced half-cycles. If driven by DC or unbalanced AC, electrolysis occurs, rapidly destroying the display.

Dedicated LCD controllers handle this automatically, but in this custom circuit, the microcontroller mustfrequently update the display, ensuring properwaveformbalancing.

We checked with an oscilloscope — and yes, that’sexactly how it works. Let’s just hope the firmware properly maintains waveform symmetry.

Current Channel Amplifier

This amplifier sits between the current transformers and the computing board.

An interestingdiscovery: sloppily soldered K73-17 capacitors — were they factory-installed, or is thisa repair job?These capacitors correct parasitic phase shifts in the current channels.

And once again — clusters ofmulti-turn trimmer resistors (SP5-2) for calibration across different current ranges.

Some of these trimmers are classic aluminum-bodied ones with a bakelite base, while others are cheaper plastic versions from the Perestroika era.

The original SovietSP5-2 trimmers were quite decent, but modernized versions look disappointingly cheap.

Why use these at all? By 2006, Bourns trimmers were readily available.

How It Works

Now, let’s break downhow the powercomputing unit operates.

By 2006, analog multipliers existed, but their accuracy and dynamic range were far from ideal. Moreover, they rely on PN-junction properties, making them highly temperature-dependent. Compensating for these effects is complex, expensive, and unstable, making it difficult to achieve the±0.1% precision required.

The Solution: A Discrete-Analog Computing Method

Instead of purely analog multiplication, this device employs ahybrid discrete-analog approach. Below is a highly simplified block diagram—many secondary components are omitted!

Core Idea:

1. Voltage signals are converted into Pulse-Width Modulated (PWM) digitalsignals.

2. Usinganalog MOS switches, they build bridge circuits, where:
   a. One diagonal receives the current signal.
   b. The other diagonal outputs a current proportional to active power.

To generate PWM signals, atriangle wave generator runs at ~550 Hz —not synchronized with the power grid (which is actually preferable).

The triangle waveform is produced using a standard integrator + comparator circuit, with amplitude stability ensured by a precision Zener diode and symmetry maintained by the SES4resistor array.

The comparator output controls the MOS switch bridge, modulating the current signal. The average output current is proportional to the instantaneous power — just like in modern DSP-based meters.

This method ischeaper and more precise than using analog multipliers.

Digitization and Frequency Conversion

Since we need highaccuracy and a widedynamic range, a simple ADC wouldn’t be enough.

Instead, the designers used a current-to-frequency converter:

• The integrator accumulates charge from the current signal.

• When the voltage exceeds a threshold, the comparator generates an output pulse.

• The charge resets, and the process repeats.

Theoutput pulse frequency isproportional to input current, achieving high accuracy.

Finally, the microcontroller simply counts pulses over a fixed time interval — producing a value proportional to total power across all three phases.

Are There Any Issues?

Almost perfect— but not quite. This design introduces a fundamental signal processing flaw:

• It samples voltage and current without filtering out high-frequency components.

• Thisviolates the Nyquist-Kotelnikov theorem, leading toaliasing effects.

A proper low-pass filter would solve this—but at 550 Hz modulation, designing one is impractical.

• A sharp roll-off filter would be complex, expensive, and woulddistortphase angles, which is critical for accurate metering.

• Instead, the designers relied on statistical averaging — assuming aliasing errors cancel out over time.

This is fine for a calibration device in a controlled lab environment — but would be problematic in real-world usage.

Oscilloscope Readings

The waveform traces below were captured directly from a real meter, at points marked with colored circles in the circuit diagram:

• Blue: Voltage signal.

• Yellow: Triangle wave modulator signal.

• Purple: Comparator output (drives the multiplier bridge).

• Green: Output of the voltage-to-frequency converter—the pulses counted by the microcontroller.

The current signal at the bridge output likely has a complex waveform, but measuring it without cutting PCB traces would betricky — so we left it untouched.

Reactive Power Measurement

To measure reactive power, the current signal must be multiplied by a 90-degree phase-shifted voltage.

Modern DSP-based meters handle this digitally,usingFIFO buffers or precomputed lookup tables.

Buthow does Energomera CE6806P do it?

It employs an oldtrick from electromechanical meters:

1. Instead of shifting voltage digitally, it uses the difference between two phase voltages.

2. A-phase current is multiplied by (B-phase voltage – C-phase voltage).

3. This naturally produces a 90-degree phase shift, allowing reactive power computation.

Limitations of This Approach

Phase imbalance completelyruins accuracy.

• Harmonicsdistort the calculation.

• Even IEC standards struggle todefine reactive power under real-world conditions with unbalanced loads.

The Giant Rotary Switch

Reactive power was calculated bymultiplying thephase currentwith thevoltage differencebetween opposite phases, naturally creating a 90-degree phase shift. Switching to reactive power mode required manuallyrotating a large rotaryswitch, which physically reconfigured transformer windings and signaled the microcontroller to adjust thescaling factor accordingly.

Conclusion

We initiallyhoped to use the Energomera CE6806Pas a reference instrument for using it on a testingsetup-stand for developing devices. But, as usual, expectations were not met.

Main Concerns:

• Too many trimmer resistors ofquestionable quality— one was faulty and had to be replaced.

• Sloppy soldering in some areas.

Ultimately, this quirky relic of the past isheading to our museum of interesting engineering solutions — a fascinating look into pre-DSP era metering techniques.