... | ... | @@ -37,6 +37,23 @@ Early ideas on how to design the LUVI UV-meter that may be helpful to see the de |
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- [DMS Application note 2: Input Configurations, Power Supplies, and Ground Loops](https://www.murata-ps.com/datasheet?/data/meters/dms-an2.pdf)
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- All models have an internal, 1- 2 microfarad, filter capacitor connected across pin 1 (+5V SUPPLY/+BATTERY) and pin 3 (5V RETURN/ –BATTERY) to attenuate high-frequency noise.
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From AN 3:
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*For 5V-powered meters, ANALOG COMMON will be approximately 2 Volts above pin 3 (5V RETURN). If the 5V power supply were to suddenly drop down to 4V, however, ANALOG COMMON would then only
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measure 1 Volt above pin 3.
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Pin 1 (+5V SUPPLY/+BATTERY), not pin 3, should always be used as the reference point if measuring ANALOG COMMON.*
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So Vcc-Vana_com = 3V (i.e. with Vcc=5V: Vanacom - Gnd = 2V).
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This 3V is used for the voltage divider to create Vref (Uref = Vrefin - Vana-com).
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Reading is ((Input_Hi - Input-Lo) / Uref) * 1000. So full scale of 2000 is twice the Uref.
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*External reference circuits should be designed so that the current drawn from pin 10 is maintained between 50 and 200 microamps.*
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|EDL-00001 | RV1 | R2 | Uref = Vref_in - Vana_com | Comment |
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| -------- | --- | -------- | --------------------------| ------- |
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| V2-0 | 5k | 17k4 | 0.25V - 0.86 V |Original, as in schematic |
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| V2-1 | 5k | [8k87](https://fr.farnell.com/neohm-te-connectivity/yr1b8k87cc/resistance-couche-metal-8k87-250mw/dp/1083357) | 0.40V - 1.32V | Allows for more sensitive sensors |
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