Introduction

This page describes the NetMeter-OMNI-8C terminal connections. 

Safety Notice

Safety procedures and additional connection information is described in the Installation Manual:

User Manuals
Title	Type	Size	Date	Note
NetMeter-OMNI-8C Installation Manual		3.4MB	2014-02-19

Connection Diagram

The connectors are:

• Supply Voltage
• A low voltage DC power supply (18-28V, 24 volt nominal) provides the power required to operate the NetMeter-OMNI
• The supply voltage terminals will work with either polarity
• ZCAN Connector
• Provides expansion capabilities for the NetMeter-OMNI to communicate with Z3 accessories
• Ethernet Connector
• This is a standard 10/100 Mb RJ45 Ethernet port that should be connected to an Ethernet switch/router using standard (CAT5/CAT5e/CAT6) network cable.
• Switch Contact Backup Voltage Terminals (V_B)
• For use with dry contact switches or KYZ contacts from pulse devices that may pulse even during power outages. The V_B terminals output a current-limited small voltage that exists even during power failure.
• Input 0 – Input 7 Terminals
• These are the input terminals for each of the 8 sensor channels. Each input can be individually configured as voltage or current mode.
• Ground Terminals
• Common ground across all inputs.

Voltage Mode Connection Diagram

Connection of Voltage Output Sensors for Self-Powered/Separately-Powered Sensor (left) or
Common NetMeter-OMNI/Sensor Power Supply (right)

Only 1 of the channels are shown. Other channels are connected in the same way.

Current Loop Connection Diagram

Connection of 4-20mA Current Loop Sensor for Separately Powered Sensor (left) or
Common NetMeter-OMNI/Sensor Power Supply (right)

Since the NetMeter-OMNI's current mode input is at near ground potential, the current loop sensor needs to be connected so that current flows from the sensors power supply positive terminal into the NetMeter-OMNI input as shown. The ground terminal on the NetMeter-OMNI provides the current return path. Any of the ground terminals may be used for this purpose.

Only 2 of the channels are shown. Other channels are connected in the same way.

KYZ and Dry Contact Devices

Many pulse output devices such as gas meters, water meters, and other types of flow meters, employ either a mechanical or electronic contact closure to assert a pulse rather than outputting a voltage or current as depicted in the previous sections. For pulse devices that output either a current or voltage pulse, they should be connected in the manner described in the previous sections.

The following description applies only to contact closure (dry contact, KYZ) devices. KYZ devices are a form of contact closure that offer both a normally-open and normally-closed option. This is depicted below:

The terminals are: K for common Y for Normally Open Z for Normally Closed

The method of connecting KYZ contacts to the NetMeter-OMNI must produce current or voltage (depending on the input configuration) when the contact is closed (or opened) and no current/voltage (or a distinctly different current/voltage) when the contact is open.

The current or voltage produced between the open and closed states must be sufficient to safely distinguish the two states. It is recommended that at least a 2V or 2mA closed/open differential be produced in order to safely detect the on/off state and reject noise.  Higher differences between the off voltage/current compared to the on voltage/current will result in higher noise immunity.

There are a number of options for connecting contact devices to the NetMeter-OMNI.  The method chosen will depend on the following considerations:

• Does the contact require a wetting current?
• Is backup power required?

No Wetting Current

The simplest ways to attach a contact to the NetMeter-OMNI is shown below:

Connection Options for a KYZ Pulse Device, Backup Powered (left), Non-backup Powered (right)

The advantage of the circuit on the left is that backup power is supplied to the contact using the V_B terminal.  This circuit is intended to be used when the sensor/meter may produce pulses even when utility power has been lost and these pulses need to be captured.  

When the contact is open, the voltage at I0 will be 0V ± some small noise voltage.  When V_B is applied to a single input channel, it can produce about 2.2V.  V_B will continue to produce a voltage even when power to the NetMeter-OMNI is temporarily lost.

Wetting Current

In some cases, mechanical contractors require a wetting current in order to function reliably. Wetting current is the minimum electric current needing to flow through a contact to break through the surface film resistance. Below are two examples:

Connection Options for a KYZ Pulse Device that Provide a Wetting Current

For either of these circuits, the resistor value (R) should be chosen so that enough current flows through the switch to generate the desired wetting current.  When configured for voltage mode, the input impedance of the NetMeter-OMNI will have negligible effect on the circuit so that R can be calculated as follows:

Here are some examples for a 24 V power supply:

Note that either normally closed (KZ) or normally open (KY) contacts may be used in either of the above cases.  The case is shown are for the default polarity of low-to-high pulse edge. The opposite switch polarity may be chosen by using the high-to-low edge setting in the “Sensor Configuration” page.