Converting Pulses to an Analog Value
March 2013
We’ve been asked hundreds of times for a device that would convert pulses to an analog voltage or current that represented a KW level. Well, finally developed such a device, called the PCL1. The PCL1 PulsetoCurrent Loop Converter receives KY pulses from a meter pulse output and converts them to a standard analog 420mA output current. The PCL1 is programmed with the 2wire pulse constant and a full scale KW value. From there each time a pulse is received, the calculation is done to calculate the instantaneous kW demand. Here’s an example:  
If a building has a 483KW maximum demand, set the Full Scale Value at 500KW. The absolute maximum is 500KW. Therefore, 500KW = 20mA. 0KW = 4mA. Resolution would be 500 / 255 or 1.961kW (or 3.922% of full scale) per step. Assume that the electric meter’s PKe Pulse value (3 Wire) is 240wh/pulse (.240kWh/pulse) Therefore the 2wire equivalent pulse value is 480 wh/pulse. Let’s say that pulses right now at this moment in time are coming at a rate of one pulse per 4 seconds and the load is steady. Conversion would be: .480 kWh X 3600 = 1728 kWsec / 4 sec = 432 kW. Output current would be 432/500 = 86.4% X 16mA = 13.824mA + 4mA = 17.824mA out. Output resolution is 16mA/256 setps or .0625mA per step. So, 256 * 86.4% = 221.184 steps of 256. Rounding off 221 X .0625mA = 13.8125mA + 4mA = 17.8125mA output. Accuracy = 99.9168% The 17.81mA output current would be fed into a device with a 420mA current input which contains a precision 250 ohm .1% resistor which converts the current into a usable voltage between 1.0VDC and 5.0VDC which is readable by the devices’ AD converter.  
In addition to converting the pulse to an instantaneous kW level, the PCL1 contains an Average output mode that can output a current that represents the calculated kW average similar to the electric meter’s Average kW calculation on a 1, 2 5, 10, 15, 30, or 60 minute average interval. The PCL1 is programmed using a free software program called the pclhost.exe and communicates using the PCL1’s USB port. In summary, the PCL1 is a simple and easy, low cost way to convert pulses to a usable analog voltage level that can be used by many systems. 

Learn more about the PCL1 PulsetoCurrent Loop Converter 