Ultrasonic Flow
A matched pair of clamp-on ultrasonic transducers measures liquid velocity and volumetric flow without placing a mechanical obstruction in the pipeline.
Energy CU-E Meter
With rising fuel costs the need for improvements in energy measurement has driven the Cadillac® Energy Measurement Systems to be acknowledged as the new industry standard.
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The Cadillac® CU-E BTU Meter is designed to measure the energy consumed in hot water heating and chilled water cooling systems. The meter is a rate and totalizing device, which is capable of calculating and displaying Volume, Energy, and Temperatures.
The Cadillac® CU-E BTU / Energy Meter measures the temperature in the feed and return lines via two RTD transmitters and from this calculates the density and enthalpy of the water. In addition, by also measuring the volume of water flowing in the system via the Cadillac® flow meter, the CU-E will then compute, display, and output the Energy consumed.
The New Industry Standard
Combining Cadillac®’s CU-T ultrasonic flow meter with advanced electronics and the capability for temperature inputs the CU-E BTU / Energy meter is quickly become acknowledged as the industry standard. Customers choose the Cadillac® CU-E BTU / Energy Meter because of proven: accuracy, dependability, consistency, maintenance and rangeability.
Technical Product Guide
CU-E Ultrasonic Energy Meter
Explore the CU-E system’s applications, operating principle, ultrasonic transducer arrangement, temperature measurement, installation requirements, published specifications and model-code options for hot-water heating and chilled-water cooling systems.
CU-E Energy Measurement
CU-E Ultrasonic Energy Meter Overview
The Cadillac Meter CU-E is a rate-and-totalizing thermal energy meter for hot-water heating and chilled-water cooling systems. It combines transit-time ultrasonic flow measurement with a matched pair of RTD temperature transmitters to calculate and display volume, temperatures, thermal-energy rate and totalized energy.
The ultrasonic flow transducers mount to the outside of the pipe. Optional strap-on temperature assemblies can provide a completely non-intrusive measurement system, making the CU-E particularly useful for retrofit projects where cutting into an operating pipe would be disruptive or impractical.
Matched Temperature Inputs
Matched RTD temperature transmitters measure the feed and return temperatures required for the thermal-energy calculation.
Energy Calculation
The CU-E combines volumetric flow, water density and the enthalpy difference between the feed and return lines to calculate thermal power and totalized energy.
System Integration
Available configurations include analog, pulse or relay outputs and RS485 Modbus RTU communication for connection to building and energy-management systems.
Where the CU-E Fits
Applications and Operating Modes
The CU-E provides a common measurement platform for heating and cooling loops where volumetric flow and temperature difference must be converted into usable thermal-energy data. It can support facility monitoring, cost allocation, system analysis and building-management integration.
Typical CU-E Applications
- Energy-consumption data for building energy-management systems, distributed control systems and district-wide monitoring networks.
- Internal energy-cost allocation across campuses, facilities, departments or individual areas of use.
- Central monitoring of heating and chilled-water system efficiency and operating performance.
- Direct energy or BTU measurement at boilers, central plants and points of use.
- Customer billing based on totalized flow and thermal-energy measurements.
- Process monitoring and thermal-efficiency optimization.
Available Calculation Modes
Heating
Positive temperature differences are totalized.
Cooling
Negative temperature differences are totalized.
Heating and Cooling
Supports systems that operate in both heating and cooling
conditions.
Charge and Discharge
Supports suitable thermal-energy storage applications.
How Energy Is Calculated
CU-E Operating Principle
1. Transit-Time Flow Measurement
Two ultrasonic transducers send acoustic signals through the pipe and liquid in opposite directions. Flow changes the travel time of the upstream and downstream signals. The CU-E electronics measure this difference to determine liquid velocity.
The measured velocity is multiplied by the effective internal cross-sectional area of the programmed pipe to calculate volumetric flow rate.
2. Temperature and Energy Measurement
Matched RTD temperature transmitters measure the feed and return temperatures. From those readings, the CU-E determines the density and specific enthalpy of the water.
The electronics combine the volumetric flow rate with the enthalpy difference between the feed and return lines to calculate thermal power and totalized energy.
Thermal-Power Calculation
P = V × ρ × (hfeed − hreturn)
| Symbol | Measurement | Meaning |
|---|---|---|
| P | Thermal power | Rate of thermal-energy transfer |
| V | Volumetric flow rate | Water volume moving through the pipe |
| ρ | Water density | Density calculated from the measured conditions |
| h | Specific enthalpy | Calculated separately at the feed and return temperatures |
CU-E System Layout
System Architecture and Connections
The CU-E system combines flow and temperature measurements within one energy-calculation platform. The electronics receive signals from the ultrasonic flow transducers and matched temperature transmitters, calculate thermal-energy values and make the configured measurements available to a building or plant control system.
Flow Transducers
A matched clamp-on transducer pair measures liquid velocity and volumetric flow.
RTD Transmitters
A matched pair measures the feed and return temperatures.
CU-E Electronics
The meter calculates flow, temperature difference, thermal power and totalized energy.
BMS or Control System
Configured analog, digital or serial outputs communicate the required measurements.
Measurement Inputs
- Matched ultrasonic flow-transducer pair
- Matched RTD temperature-transmitter pair
- Programmed pipe dimensions and material
- Application and fluid configuration data
Available Output Configurations
- Optically isolated 4–20 mA analog output
- Digital pulse or relay output
- Combined analog and digital output configurations
- RS485 Modbus RTU communication, where specified
Measurement Integrity
Installation and Site Selection
Installation quality is critical to reliable transit-time ultrasonic measurement. Because the existing process pipe acts as both the flow containment and the measurement spool, location, flow profile, pipe condition, sensor orientation and mounting accuracy can directly affect signal quality and performance.
Select a stable section of completely full pipe and confirm that the available straight run is appropriate for the actual upstream and downstream disturbances.
Transducer Location Checklist
- Choose a pipe section that remains completely full during operation.
- Provide at least 10 pipe diameters upstream and 5 diameters downstream under typical conditions.
- After a pump, control valve or double pipe bend, as much as 30 upstream pipe diameters may be required.
- Confirm that the pipe skin temperature is within the transducer temperature rating.
- Prefer pipe surfaces that are free from excessive scale, rust, debris and corrosion.
Horizontal Pipe Orientation
3 or 9 o’clock
Preferred side positions
Mounting the transducers near the sides of a horizontal pipe helps avoid sediment collecting at the bottom and bubbles or air pockets accumulating at the top.
Pipe liners should be properly bonded to the pipe wall. Significant internal coating may interfere with acoustic signal transmission.
Pipe-Diameter Guidance
Ultrasonic Transducer Mounting Methods
Transit-time ultrasonic transducers may be arranged using W, V or Z acoustic paths. The traditional CU-E guidance assigns the mounting method by approximate pipe diameter. The final method and exact transducer spacing must be determined for the actual pipe, transducer set and application.
Each configuration changes the number of times the ultrasonic signal crosses the pipe. Smaller pipes generally use a longer multi-pass acoustic path, while larger pipes use a more direct path.
W
W Mounting
Approximately ¾–4 in.
↘ ↗ ↘ ↗
Multiple signal traversals increase the acoustic path length in smaller pipe. Both transducers are mounted on the same side of the pipe.
V
V Mounting
Approximately 4–16 in.
↘ ↗
A two-pass acoustic path is used, with both transducers positioned on the same side of the pipe.
Z
Z Mounting
Approximately 16 in. and larger
↘
A direct single-pass signal path is used, with the transducers positioned on opposite sides of the pipe.
| Method | Traditional Pipe-Diameter Guidance | Acoustic Path |
|---|---|---|
| W | ¾–4 in. | Multiple traversals |
| V | 4–16 in. | Two-pass path |
| Z | 16 in. and larger | Direct single-pass path |
CU-E Electronics
General Specifications
The CU-E combines remote energy-calculation electronics with a matched pair of clamp-on ultrasonic flow transducers and matched temperature transmitters. Published performance remains dependent on correct application, pipe data, flow profile, sensor placement and installation quality.
| Parameter | Published CU-E Specification |
|---|---|
| System Components | Remote electronics, one matched pair of clamp-on ultrasonic transducers and one matched pair of temperature transmitters. |
| Measurement Technology | Digital-correlation transit-time ultrasonic flow measurement with energy-computation features and temperature inputs. |
| Display | Four-line, 16-character backlit LCD displaying instantaneous energy, totalized energy, velocity and operating status. |
| Programming | Meter configuration through the integral keypad. |
| Flow Range | 0 to ±40.0 ft/s (0 to ±12.0 m/s), with bidirectional flow measurement. |
| Energy-System Accuracy | Typically ±2.0% of reading. Actual performance is also dependent on the flow profile, application conditions and installation. |
| Repeatability | 0.2% of reading. |
| Flow-Transducer Temperature Range | −40°F to +250°F (−40°C to +121°C). |
| Electronics Temperature Range | −4°F to +130°F (−20°C to +60°C). |
| Standard Housing | NEMA 4X (IP65) ABS plastic enclosure. |
| Outputs and Communication | Available configurations include optically isolated 4–20 mA, digital pulse or relay output and RS485 Modbus RTU communication. |
| Published Power Options | 90–132 Vac, 50/60 Hz; 190–250 Vac, 50/60 Hz; or 20–30 Vdc, according to model code. |
Configure the CU-E
CU-E Model-Code Selection
The CU-series ordering structure identifies the measurement function, power supply, output configuration, temperature option, installation configuration, cable length and transducer mounting arrangement. The table below consolidates the CU-E-relevant choices published in the legacy product literature.
| Model-Code Field | Code | Published Meaning |
|---|---|---|
| Series | CU | Cadillac ultrasonic flow meter |
| Measurement | E | Digital-correlation transit-time measurement with energy-computation features and temperature inputs |
| Power Supply | A | 90–132 Vac, 50/60 Hz — standard |
| B | 190–250 Vac, 50/60 Hz | |
| C | 20–30 Vdc | |
| Output Configuration | A | 4–20 mA output or digital pulse/relay output |
| B | 4–20 mA output and digital pulse/relay output | |
| C | 4–20 mA, digital pulse/relay and RS485 Modbus RTU | |
| Temperature Option | B | Matched pair of 100-ohm temperature transmitters |
| Configuration | D | Dedicated |
| P | Portable; digital output not available | |
| Area Classification | A | General-purpose area classification |
| Transducer Cable | 06 / 10 / 15 / 20 / 30 | Cable length in metres; 6 metres published as standard |
| Transducers and Mounting | R1 | Transducers with pipe-size mounting rack |
| R2 | Transducers with mounting rack for approximately ½–2 in. pipe | |
| R3 | Transducers only for approximately 40–200 in. pipe | |
| R4 | Transducers with round TruClamp for approximately ½–2 in. pipe | |
| R5 | Transducers only, without a mounting-rack assembly |
Prepare Your Application
CU-E Selection Guidance
A complete application review helps Cadillac Meter confirm the correct CU-E electronics, transducers, temperature assemblies, mounting hardware, power supply and output configuration. Gather the following information before requesting a quotation.
Process and Pipe Information
- Heating, cooling, combined or charge/discharge application
- Liquid type and expected suspended solids or entrained air
- Pipe outside diameter, wall thickness, material and liner
- Minimum, normal and maximum flow rates
- Feed and return temperature ranges
- Pipe surface condition and accessibility
Installation and Output Information
- Available upstream and downstream straight run
- Nearby pumps, control valves, bends, tees or other disturbances
- Distance from the electronics to the flow and temperature sensors
- Available power supply
- Required 4–20 mA, pulse, relay or RS485 Modbus RTU outputs
- Area classification and enclosure requirements
CU-E Technical Resources
Review the Complete Technical Guide
Download the consolidated CU-E guide for product information, operating principles, installation guidance, specifications and model-code details, or contact Cadillac Meter for application-specific selection support.