The eGauge Pulse Sensor (EPS) can be used to monitor a dry contact pulse output from many different types of devices, but there's generally some additional configuration needed to convert a simple pulse count into meaningful measurements. In this article we'll discuss how to configure a formula register to make that conversion as well as some options for viewing the data.
Setting up the Registers
When logging pulse data, two registers are needed. The first keeps track of the pulse count and the second converts the pulse tally into meaningful data.
Step 1: Scan your installed EPS Pulse Sensor with CTid and add a Sensor register to record the pulses:
- Note: This first register will simply record the number of pulses that the equipment has generated.
Step 2: Add a formula register to convert the Pulse count to the actual measurement:
In the formula register, the Pulse Count register added in step 1 should be multiplied against the constant value from the pulse generating equipment. The meter constant is the part of the formula that defines what each pulse is ‘worth’. This information is typically found in the documentation or hardware specs for the pulse generating equipment.
Example formula: Volumetric flow (gas, water, etc.)
Create a formula register to calculate the volumetric flow from the pulse count. The formula register contents should be: $"Pulse Register" * constant * conversion factor where Pulse Register is the register name of the register recording the pulse count, and constant is the flow meter constant factor. conversion factor is optional and used if the constant value needs to be converted to cubic meters from another unit type.
The m3_per(unit) function can be used to calculate the conversion factor. This function returns the factor by which a quantity in the specified unit needs to be multiplied by to get the same quantity in cubic meters (m³). unit may be one of "cm3" (cubic-centimeter), "in3" (cubic-inch), "pint", "liter", "gallon" (US gallon), "ft3" (cubic foot), "barrel", or "acre-foot".
- eGauge formula register setup in the classic interface includes only cubic meters as the unit for volumetric flow.
- If the constant for the equipment is expressed in a unit other than cubic meters, the formula should be multiplied by a conversion factor to convert the unit to cubic meters. Later, when setting up the chart item in the modern interface for visualization the unit can be changed.
Example formula: Pulse output energy meters
The formula register contents should be: $"Pulse Register" * constant * 3600 where Pulse Register is the register name of the register recording the pulse count, and constant is the meter Wh constant factor (effectively, in watt-hours what one pulse indicates or "Wh-per-pulse"). The below screenshot shows the calculation for a single pulse representing 5.3 watt-hours:
Math behind the formula register
The reason 3,600 is multiplied by the Wh-per-pulse is due to the meter reading data at second-granularity and there being 3,600 seconds in one hour. For example, if there is a meter constant of "1" (meaning 1 pulse is 1 Wh), when the eGauge meter receives 1 pulse, it will record "1" at that second in time, which will show as 1 watt during that 1 second it was detected (1 watt-second of energy). To convert watt-seconds to watt-hours, we multiply by 3,600 seconds.
If a single pulse represents kWh rather than Wh, the formula will need to be multiplied by 1,000, such as:
$"Pulse Register" * constant * 3600 * 1000
- Pulse meters change output state each pulse; that is, the output goes from open to closed to indicate a single pulse, then closed to open to indicate the next pulse, and alternates continuously for each pulse.
Step 3: Save the changes to the configuration. New registers will begin recording data moving forward.
Visualizing Pulse Data
- Requires firmware version 4.7 or later.
Visualizing pulse data on the eGauge Chart view is best done using a Bar chart item.
Pulse output is different than other types of signals in the sense that a pulse happens quickly and depending on how often the third party hardware generates a pulse there can be quite a lot of time elapsed between detected pulses.
Pulse output data visualized as a Curve can be spiky and can show the total accumulation over the entire time period shown in the Chart view:
The same 15 minute period visualized as a Bar chart item is easier to interpret and provides more granular data on the chart:
Defining a Bar Chart item for Pulse data
Bar Chart items are available in firmware v. 4.7 and later. For more complete information regarding chart customization please see: Customizing the Chart View
After configuring the appropriate registers to count pulses and do the needed calculations, add a new chart item to your chart view as shown:
- Type of item: Set to Bar
- Value to Graph: Choose the formula register calculating the measurements that were set up in the first steps of this article.
- Advanced options: Check this box to display the unit dropdown to change the unit type. If left set to ‘auto’ the unit will be chosen based on the locale.