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Maximum Demand Indicator Solutions from China Suppliers and Factory - Bimetallic Movement Options
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Measuring Range
Maximum Demand Indicator (MDI) — Overview
Maximum Demand Indicator (MDI) is a panel mount meter. The thermal/time characteristics of MDI meters can monitor the most economic use of cable, protective devices and transformers. It indicates mean RMS current in the circuit within a given period of time and also records the maximum RMS current. Combining a moving-iron measuring system enables measurement of instantaneous values.
MDI Categories
With Bimetallic Movement
With Moving-Iron Ammeter
With Alarm Relay
The demand value is indicated by a black moving pointer. The maximum demand value is indicated by a red slave pointer, which can be resumed by a reset knob. It can be lead-sealed for prevention of unauthorized reset.
Technical Specifications
| Parameter | Specification |
|---|---|
| Thermal Time Delay | 15 minutes |
| Accuracy Class | 3.0 (Precise reading starts from 25% of full scale) |
| Overload — Continuous | 1.2 × rated current |
| Overload — Short Duration | 10 × rated current for 1 second |
| Overload — With Saturating CT | 20 × rated current for 1 second |
| Power Consumption | < 3 VA |
MDI Types
Type A
Maximum Demand Indicator with Bimetallic Movement
Measures the maximum load average value, indicated by the black pointer.
Type B
Combined MDI with Moving-Iron Ammeter
Measures maximum average load value (black horizontal pointer) and transient value (black vertical pointer). Accuracy class: 1.5.
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Temperature Ranges
🌡️
Operating Temperature
-20°C to +40°C
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Storage Temperature
-40°C to +70°C
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Insulation Test
⚡ Test Voltage: 2 kV RMS for 1 minute at 50 Hz frequency.
All requirements conform to IEC 61010-1.
All requirements conform to IEC 61010-1.
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Frequently Asked Questions
Q
What is a Maximum Demand Indicator (MDI) and what is it used for?
A Maximum Demand Indicator (MDI) is a panel mount meter designed to monitor and record the maximum RMS current in a circuit over a given period of time. It helps ensure the most economic use of cables, protective devices, and transformers by tracking average and peak load values.
Q
How many types of MDI meters are available and how do they differ?
MDI meters are available in three categories: with bimetallic movement, with moving-iron ammeter, or with alarm relay. Type A (bimetallic) measures maximum average load value, while Type B (combined with moving-iron ammeter) additionally measures instantaneous transient values with an accuracy class of 1.5.
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What is the thermal time delay of the MDI meter?
The thermal time delay of the MDI meter is 15 minutes. This delay reflects the thermal/time characteristics used to calculate the mean RMS current over the defined demand period.
Q
What overload capacity do MDI meters support?
MDI meters support continuous overload of 1.2 times the rated current. For short durations, they can handle 10 times the rated current for 1 second. When used with a saturating CT, the overload capacity increases to 20 times the rated current for 1 second.
Q
What are the operating and storage temperature ranges for these panel meters?
All panel meters operate trouble-free at ambient temperatures between -20°C and +40°C. For storage, the acceptable temperature range is -40°C to +70°C, making them suitable for a wide range of environmental conditions.
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What insulation standard do these MDI meters comply with?
The MDI meters are tested with a dielectric withstand voltage of 2 kV RMS for 1 minute at a frequency of 50 Hz. All insulation requirements fully conform to the international standard IEC 61010-1.