EM-203A is a low-voltage monitor designed for 12 V battery-powered systems. It continuously monitors the battery voltage and activates an alarm output when the voltage falls below the adjustable threshold.
The adjustable alarm delay prevents short voltage dips from causing unnecessary alarms. Recovery hysteresis is also adjustable, helping prevent repeated switching when the battery voltage is close to the alarm threshold.
The EM-203A can be connected directly to a 12 V battery system. The low-voltage alarm threshold can be adjusted between 10 and 12 V.
When the measured battery voltage falls below the selected threshold, the alarm delay begins. If the voltage remains below the threshold for the selected delay period, the alarm output is activated.
The alarm activation delay can be adjusted from 0 to 5 minutes. This allows short voltage drops caused by motor starting, solenoid operation or other temporary loads to be ignored.
The recovery hysteresis can be adjusted from 0 to 2 V. Once an alarm is active, it is cleared immediately when the battery voltage rises above the alarm threshold plus the selected hysteresis value.
For example, with an alarm threshold of 11 V and hysteresis of 1 V, the alarm is activated after the selected delay if the voltage remains below 11 V. The alarm is cleared when the voltage rises above 12 V.
The transistor output can be configured for either flashing or continuous operation. Flashing mode can be used for a visual warning, while continuous mode is suitable for operating an external alarm device or control input.
An external LED indicator can be connected directly between pins 3 and 4. A small relay or indicator lamp can be connected using pins 1 and 3, provided that the output load remains within the specified 50 mA limit.
The EM-203A has low internal current consumption to minimize battery discharge during continuous monitoring. Typical current consumption depends on the selected operating state and alarm mode.
The unit can be mounted using a 3 mm screw or a suitable holder. Installation in a DIN-rail base is also possible.
| Application | 12 V battery voltage monitoring |
|---|---|
| Operating voltage | 8–28 VDC |
| Standby current | 0.9 mA |
| Current consumption, flashing alarm | 1.2 mA |
| Current consumption, continuous alarm | 1.9 mA |
| Maximum output current | 50 mA |
| Low-voltage threshold | Adjustable 10–12 V |
| Recovery hysteresis | Adjustable 0–2 V |
| Alarm activation delay | Adjustable 0–5 min |
| Alarm reset delay | No intentional delay |
| Alarm output mode | Flashing or continuous |
| Operating ambient temperature | −40 … +60 °C |
| Mounting options | 3 mm screw, holder or DIN-rail base |
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