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Measurement & Control News for November

 
 70 Years of Power & Process Measurements                                                              November 2010
 
 
In This Issue:
  
 Ground Detection Voltmeter 
 
 Ethernet Network Interface
 
• Wiring Inspection & Test 
   Tool 
 
• Universal Signal Conditioner 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Measurement & Control News is a newsletter highlighting products, applications and information of interest to instrumentation users.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Visit weschler.com for:
Digital Meters
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Bargraph Meters
Controllers
Sensors & Transducers
Signal Conditioners
Test Equipment
 
We carry Weschler products and products from 50 of the leading equipment brands.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Weschler Instruments
16900 Foltz Parkway
Cleveland OH 44149 USA
 
phone:   800-903-9870
             440-378-6580
fax:        800-903-9590
             440-238-0660    
 
 
Offices in OH, NY, FL & TX
 
 
 
 
 
 
 
 
Ground Detection Voltmeter
A ground detection voltmeter is used to monitor a floating battery bank for inadvertent grounding of either side.  Historically, a center zero analog meter has been used for this application. The meter typically has a 500uA or 1mA DC movement, with a voltage scale of 100-0-100 for a 72V battery bank, 150-0-150 for a 125V battery bank or 300-0-300 for a 250V battery bank. Two high value resistors are installed across the battery and the center tap connected to the grounded meter.  A low impedance to ground on either side of the battery causes the meter to move off center, indicating both the severity of the fault and which side it is on. The resistor value is selected so that a direct short to ground reads the full voltage.
Ground Detector Bargraph Meter
 
A digital bargraph meter will easily replace the analog meter in this circuit, often mounting in the same panel cutout.  The bargraph meter provides both a digital readout and a highly visible bar to indicate a fault situation.  To help spot a problem more quickly, a tricolor bar can be configured to change color when a threshold level is exceeded in either direction. The bargraph meter offers several other improvements over the analog meter.  It may include relay outputs to activate a service alert or alarm at specific fault levels. It may also have a digital interface for remote monitoring through a network or SCADA system.     Digital Bargraph Meters   
 
Network Interface for Instrument Cluster 
Laurel Electronics has introduced a new Ethernet interface that simplifies networking for a cluster of panel meters. The Laureate Ethernet-to-RS485 Device Server Board plugs into a host Laurel digital panel meter, counter or timer and provides a 10/100Base-T connection on an industry-standard RJ45 jack. It also has an RJ11 jack for interface to downstream meters on a RS485 bus, which can support up to 31 meters.  This allows a group of Laurel digital meters to access the internet through a single Ethernet connection.  Dual RJ11 connectors on each RS485 interface permit daisy-chaining using commercial 6-wire RJ11 data cables.
Laurel Ethernet Network
The Modbus TCP protocol is fully supported. Conversion to Modbus TCP is provided transparently so that an Ethernet application program can use the Modbus TCP protocol while the meters use the Modbus RTU or Modbus ASCII protocol. The Laurel ASCII protocol can also be used if the only devices on the data line are Laureate meters.  Laurel's Node Manager software is shipped with each Ethernet interface. This Windows-based application automatically discovers & configures all Laurel nodes on a LAN or WAN, plus any meters connected to the nodes. (A node is any meter with an Ethernet interface, including the host meter for the Ethernet-to-RS485 Device Server Board).    Laurel Panel Meters      
 
 
Wiring Inspection & Test Tool
Amprobe Wiring InspectorThe new Amprobe INSP-3 Wiring Inspector Tester quickly verifies building wiring compliance to electrical code.  This tester measures voltage drop under load to identify problems with connections, splices and conductor quality.  The operator can select a load of 0, 10, 15 and 20 amps, which is constant, regardless of line voltage.  The INSP-3 checks ground quality for safety and ability to support sensitive electronic equipment. Voltage under load, voltage drop, hot/neutral voltages and ground impedance are all presented on a single operator display to save time.  No need to scroll thru multiple screens.
This versatile meter also tests GFCI and AFCI operation. All load tests are done without tripping circuit breakers or blowing fuses.  The handheld Amprobe INSP-3 operates from a single 9V battery and comes with carrying case and 120V AC test plug.
 
Universal Signal Conditioner 
Red Lion Universal Signal ConditionerRed Lion has consolidated a line of signal conditioning modules into one model with the introduction of the IAMS Universal Signal Conditioner.   This field-configurable device accepts process, DC current, DC voltage, thermocouple, RTD, potentiometer and linear resistance inputs, allowing it to be connected to most common sensors. The IAMS features well over 100 combinations of input to output (range and function) configurations.  The power supply is also universal, operating over a wide range: 21.6-253 VAC or 19.2-300 VDC. 

Add the optional programming display and the IAMS is easily set up through menu style programming. Only one programming unit is required to set up multiple devices. The module can store programming from one unit and load it to a second unit, reducing set-up time for multiple installations. The removable programming unit can also be used to provide a display of the process variable when it is not being used for programming.

The basic full scale accuracy exceeds 0.1%, depending on the range and scale factor. Onboard non-volatile memory stores scaling values for future recall. All units come factory precalibrated for all input and output ranges, but can be custom scaled in the field.  The unit’s environmental operating range is -20º C to 60º C.  DIN rail mounting saves time and panel space.  The setpoint option allows dual setpoint control capability through two Form A relays. The analog output option provides a retransmitted analog signal (mA or DCV).  Data Sheet     Other Red Lion products