0102030405
China Maximum Demand Indicator Suppliers - Bimetallic Movement & Combined Ammeter Factory Products
1
Measuring Range
1.1 Maximum Demand Indicator
1.1.1 Maximum Demand Indicator with Bimetallic Movement
1.2 Maximum Demand Indicator
1.2.1 Combined Maximum Demand Indicator with Bimetallic Moving-Iron Ammeter
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 can measure the instantaneous value.
- MDI can be divided into 3 categories: with bimetallic movement, with moving-iron ammeter, or with alarm relay.
- The demand value is indicated by the black moving pointer.
- The maximum demand value is indicated by the red slave pointer, which can be resumed by 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 times rated current |
| Overload — Short Duration | 10 times rated current for 1 second |
| Overload — With Saturating CT | 20 times rated current for 1 second |
| Power Consumption | < 3 VA |
MDI Categories
Category A
Maximum Demand Indicator with Bimetallic Movement — Measures the maximum load average value (indicated by black pointer).
Category B
Combined Maximum Demand Indicator with Moving-Iron Ammeter — Measures maximum average load value (indicated by black horizontal pointer) and transient value (indicated by black vertical pointer). Accuracy class is 1.5.
2
Temperature Ranges
🌡️
Operating Temperature
-20°C to +40°C
📦
Storage Temperature
-40°C to +70°C
- All panel meters can operate trouble-free at room temperatures ranging from -20°C to +40°C.
- Storage temperature range: -40°C to +70°C.
4
Insulation Test
🔒
The test voltage is 2 kV RMS for 1 minute with a frequency of 50 Hz.
All requirements conform to IEC 61010-1.
All requirements conform to IEC 61010-1.
?
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 the thermal/time characteristics of electrical circuits. It indicates the mean RMS current within a given period of time and records the maximum RMS current, helping to ensure the most economic use of cables, protective devices, and transformers.
Q
How many categories of MDI are available, and what are the differences?
MDI meters are available in 3 categories: (A) with bimetallic movement — measuring maximum load average value; (B) combined with moving-iron ammeter — measuring both maximum average load and transient values with an accuracy class of 1.5; and (C) with alarm relay for alert-based monitoring.
Q
What do the black and red pointers on the MDI represent?
The black moving pointer indicates the current demand value in real time, while the red slave pointer records and displays the maximum demand value reached. The red pointer can be reset using the reset knob, and the meter can be lead-sealed to prevent unauthorized resetting.
Q
What is the thermal time delay of the MDI meter, and why does it matter?
The MDI meter has a thermal time delay of 15 minutes. This delay reflects the thermal characteristics of cables and transformers, allowing the meter to accurately represent the average load over a defined period rather than reacting to instantaneous peaks, which is critical for proper equipment protection and load management.
Q
What overload capacity does the MDI meter support?
The MDI meter supports continuous overload at 1.2 times the rated current. For short durations, it can handle 10 times the rated current for 1 second. When used with a saturating CT, it can withstand 20 times the rated current for 1 second.
Q
What safety and insulation standards does the MDI meter comply with?
The MDI meter complies with IEC 61010-1 standards. The insulation test is performed at 2 kV RMS for 1 minute at 50 Hz frequency. The meter operates reliably within a temperature range of -20°C to +40°C and can be stored between -40°C and +70°C.