“When the DMS-EB-RMS application board is soldered to a 2V input, 31⁄2-digit DMS-30 series meter, the meter enables the meter to display the true RMS value of AC voltage up to 750V with a resolution of 1V. When the circuit board is soldered to a DMS-30 meter with a 200mV input, it can display an AC voltage of up to 199.9V with a resolution of 0.1V. The DMS-EB-RMS board will work with an LED display (DMS-30PC) or a 5V-powered LCD display (DMS-30LCD).
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When the DMS-EB-RMS application board is soldered to a 2V input, 31⁄2-digit DMS-30 series meter, the meter enables the meter to display the true RMS value of AC voltage up to 750V with a resolution of 1V. When the circuit board is soldered to a DMS-30 meter with a 200mV input, it can display an AC voltage of up to 199.9V with a resolution of 0.1V. The DMS-EB-RMS board will work with an LED display (DMS-30PC) or a 5V-powered LCD display (DMS-30LCD).
As shown in Figure 1, a 1000:1 voltage divider composed of resistors R1 (988k), R2 (988k) and R3 (1.98k) is used to attenuate the AC input to a level acceptable to U1. U1 is a precision integrated circuit AC-rms converter whose DC output is directly applied to the input of DMS-30.
For example, suppose that 120Vrms, 60Hz AC power cord input is applied to terminals 1 and 3 of TB1. This input is divided into 0.120Vrms and then applied to U1. If the input range of the selected DMS-30 meter is ±2V (suffix -1), the display will read “120” (1Vac resolution). If the input range of the selected DMS-30 meter is ±200mV (suffix -0), the display will read “120.0” (decimal point DP3 is enabled by shortening the weld SG1).
Power DMS-EB-RMS
As stated in the DMS-EB-RMS data sheet, a dedicated, transformer-isolated +5V power supply must be used to power the DMS-EB-RMS and its meters to ensure safe operation when measuring AC power input signals. The breakdown voltage rating of the transformer must always be higher than the AC input under test. DMS-EB-RMS has no isolation between the AC input signal and the 5V Return terminal of the meter. Please be extra careful when connecting any AC power source as an input signal to the DMS-EB-RMS. Never ground the 5V Return terminal of the DMS-EB-RMS (chassis), as this may invalidate any safety grounding and place the system’s +5V power supply and all related circuits at a dangerous high potential of the AC power supply.
If the input signal is transformer-coupled or electrically isolated from the AC power cord, only the above precautions may deviate. The output of a current transformer (used for AC amperage measurement) is an example of an AC signal, which usually exceeds the aforementioned isolation requirements.
When the DMS-EB-RMS application board is soldered to a 2V input, 31⁄2-digit DMS-30 series meter, the meter enables the meter to display the true RMS value of AC voltage up to 750V with a resolution of 1V. When the circuit board is soldered to a DMS-30 meter with a 200mV input, it can display an AC voltage of up to 199.9V with a resolution of 0.1V. The DMS-EB-RMS board will work with an LED display (DMS-30PC) or a 5V-powered LCD display (DMS-30LCD).
As shown in Figure 1, a 1000:1 voltage divider composed of resistors R1 (988k), R2 (988k) and R3 (1.98k) is used to attenuate the AC input to a level acceptable to U1. U1 is a precision integrated circuit AC-rms converter whose DC output is directly applied to the input of DMS-30.
For example, suppose that 120Vrms, 60Hz AC power cord input is applied to terminals 1 and 3 of TB1. This input is divided into 0.120Vrms and then applied to U1. If the input range of the selected DMS-30 meter is ±2V (suffix -1), the display will read “120” (1Vac resolution). If the input range of the selected DMS-30 meter is ±200mV (suffix -0), the display will read “120.0” (decimal point DP3 is enabled by shortening the weld SG1).
Power DMS-EB-RMS
As stated in the DMS-EB-RMS data sheet, a dedicated, transformer-isolated +5V power supply must be used to power the DMS-EB-RMS and its meters to ensure safe operation when measuring AC power input signals. The breakdown voltage rating of the transformer must always be higher than the AC input under test. DMS-EB-RMS has no isolation between the AC input signal and the 5V Return terminal of the meter. Please be extra careful when connecting any AC power source as an input signal to the DMS-EB-RMS. Never ground the 5V Return terminal of the DMS-EB-RMS (chassis), as this may invalidate any safety grounding and place the system’s +5V power supply and all related circuits at a dangerous high potential of the AC power supply.
If the input signal is transformer-coupled or electrically isolated from the AC power line, only the above precautions may deviate. The output of a current transformer (used for AC amperage measurement) is an example of an AC signal, which usually exceeds the aforementioned isolation requirements.