ezeio2:installation:inputs

There are eight (8) inputs on the ezeio hardware. More inputs can be added using the ezeio expansion modules. Other types of inputs can be added usign third party devices connected via Modbus, CAN or SDI-12.

The ezeio inputs are compatible with a wide variety of sensors, either directly or thought the use of an amplifier or transmitter.

These common industry standard sensor outputs are directly supported by the ezeio

  • Voltage (0-1V, 0-5V or 0-10V)
  • Current (0-20mA or 4-20mA - often referred to as Current Loop)
  • Pulse rate/count or resistive/switch.

Some examples of sensors with these types of outputs are;

  • CO2 sensors with 0-10V output (the voltage correspond to ppm of gas concentration)
  • Pressure transmitters with 4-20mA output (the current corresponds to the pressure)
  • Thermistors (the resistance corresponds to temperature)
  • Flow meters (provides a pulse for a specified volume)

The ezeio easily converts the measured voltage, current, resistance or pulse rate to units related to the sensor type (ppm, kPa/psi, °C/°F, L/h etc..).

The ezeio inputs are individually configurable for the following modes:

0-10V Measuring an external voltage between 0 and 10V relative to ground (default)
0-30mA Measuring a current, 0-30mA, typically used with 4-20mA sensors
Resistive Measuring an external resistance (between the input and ground)
Thermistor Like Resistive, but outputting the temperature
Pulse Measuring the frequency and count of pulses

Do not exceed the rated voltage or current for the inputs.

With the input set to measure 0-10V, the input will be set to high impedance mode, and the input value will reflect the voltage on the input in mV (0-10000 mV). The impedance when in 0-10V mode is 69200 Ohm.

Input setting : 0-10V
Input range 0 - 10240mV
Resolution 2.5mV
Accuracy +/- 5mV
Impedance 62900 Ohm
Excitation no

Changing the range for higher voltages

If you need to monitor a higher voltage than 10V, you can connect an in-line 270kOhm resistor. This will extend the input range to 0-54.2V with a resolution of 13.24mV. We do not recommend this method for voltages exceeding 50V. For higher voltages, use a suitable voltage transducer.

When set for 0-30mA, the input will be internally connected to ground via a 200 Ohm resistor. The input scaling switches to reflect micro-Ampere though the resistor.

This mode is commonly used for industry standard 4-20mA sensors.

Input setting : 0-30mA
Input range 0 - 30000µA
Resolution 12.5µA
Accuracy +/- 25µA
Impedance 200 Ohm
Excitation no

When the input is set to monitor an external resistance, an internal 4780 Ohm resistor is enabled to connect the input to the internal +5V. This allows a small current to run through the external resistor, and this allows the ezeio to measure the voltage and convert it to resistance.

An internal reference is used to find the ratio and more accurately calculate the external resistance in Ohms.

Input setting : Resistance
Input range 0 - 1MOhm
Resolution Varies over the range
Accuracy Better than 2% in the 200Ohm - 100kOhm range
Impedance not applicable
Excitation yes, 4870 Ohm to 5V (1mA short circuit)

A thermistor is a resistor that changes resistance with temperature. The input setting is very similar to when an external resistor is used, but the input value is recalculated using the Steinhart-Hart math to reflect a temperature.

There are five different types of thermistors supported:

Type Typical application Beta
10k, Type 2 Indoor temperatures, 0°C to +60°C (30-140°F) 3800K
10k, Type 3 Indoor temperatures, -5°C to +60°C (20-140°F) 3500K
10k Outdoor temperatures, -25°C to +60°C (-10-140°F) 3380K
2k2 Refrigeration systems, -40°C to +20°C (-40-70°F) 3800K
100k Heating systems, boilers, +50°C to +150°C (120-300°F) 4000K
PT1000 1) Wide range, -70°C to +370°C (-90-700°F) (reduced resolution) n/a

The thermistors will continue to work outside the above temperatures, but the accuracy will be lower at higher and lower temperatures.

The PT1000 type sensor will work over a very wide temperature range, but lower resolution than a thermistor (a few °K typically).

Input setting : Thermistor
Input range 20000 to 65000 (°K x100)
Resolution Varies over the range
Accuracy 0.5°K when around 10kOhm
Impedance not applicable
Excitation yes, 4870 Ohm to 5V (1mA short circuit)

The ezeio inputs does not directly support PT100 or Thermocouple type sensors. If you need to use these types of sensors, use a signal conditioner to convert the signal to 0-10V or 4-20mA, or use a digital expander with suitable inputs.

When set to monitor pulses, the ezeio input can be configured either in resistive mode or in 0-10V mode. If the pulse source is a passive switch, like a KYZ output or a opto-coupler transistor output, the resistive mode is suitable and will apply enough current through the circuit for the ezeio to detect the pulses. If the pulse source is active, outputting a switched voltage, the 0-10V input mode is more suitable.

The maximum frequency that can be detected reliably by the ezeio is 400Hz.

If the pulse interval is larger than 20s (0.05Hz), the ezeio will consider this as no pulses (0 Hz).

Input setting : Pulse
Input range 50-400000 mHz (mHz = Hz x 1000)
Resolution
Accuracy
Impedance not applicable
Excitation optional

The register value has the unit mHz (Hertz x1000). To convert to other units, use these examples:

Input Desired output Conversion
Pulses per second (Hz) r(x,x)*0.001
Pulses per minute (ppm) r(x,x)*0.06
Pulses per hour (pph) r(x,x)*3.6
2L/pulse Liters per minute 2*r(x,x)*0.06
12 pulses per Liter Liters per hour 1/12*r(x,x)*3.6
14 gal/pulse Gallons per hour 14*r(x,x)*3.6
100 pulses per kWh kW 1/100*r(x,x)*3.6
0.5kWh per pulse W 0.5*r(x,x)*3600


1)
PT1000 is not technically a thermistor, but works similarly
  • ezeio2/installation/inputs.txt
  • Last modified: 2019-09-02 19:27
  • by andreh