Microflex 101-0028 Field Tools Loop Power Portable 24 Volt Power Supply User Manual

Field Tools

Loop Power                               101-0028

Operation & Specifications Manual

General Description

The Field Tools Loop Power provides a portable power source for commissioning and calibrating loop devices. It is a fully contained power source that takes the low voltage from three “AAA” alkaline batteries and increases it to a highly filtered 24 volts DC. Using batteries for the power source eliminates isolation on concerns as well as the need for a power connection on to AC or a USB port. The voltage conversion is done using a high efficiency switching DC- DC converter to maximize battery life. Simply connect the two mini-clips to the power input of your loop powered device. A push-bu on is used to enable or disable the 24 volts while a status LED indicates the active operating mode. An internal 250 ohm loop resistor, HART protocol modem clip points, and current meter leads with standard banana jacks make Loop Power a complete setup solution for 4-20 mA devices.

620-0012 R3 © Microflex, LLC 2015-2021

Features

• Highly filtered 24 volt power source for loop devices
• Up to 30mA capacity, perfect for 4-20mA transmitters
• Battery power eliminates galvanic isolation concerns
• Includes an internal 250 ohm loop resistor to allow for HART protocol
• HART modem mini-grabber clip points for easy modem connection to the loop
• Mini-clips for easy connection to the loop device power terminals
• All connection leads included – no need for extra test leads or alligator clips
• Long battery life, greater than 6 hours continuous at 12mA load
• Status LED indicates when batteries are getting low
• Able to maintain output even with weak batteries to maximize battery life
• Uses easy to find low cost standard “AAA” alkaline batteries
• Short circuit protection disconnects the output if shorted
• Compact durable enclosure stands up to rugged field use

Safety Considerations

Warning
To prevent loss or injury only use Loop Power as specified in the manual.

• Never apply more than 30 volts between any two terminals or leads.
• Never operate with the battery cover and cover screws removed or loose.
• Do not use if the leads become damaged.
• Disconnect all connections before removing the battery cover.
• Do not operate around explosive gas, vapor, or dust.
• Contact Microflex, LLC for servicing or repairs.

Replacing or Installing Batteries

**** Always disconnect all leads and connections to Loop Power before removing the battery cover.

1. Loosen and remove the two cover screws and cover to access the battery holder.
2. Remove and replace all three “AAA” alkaline batteries.
3. Replace the cover and screws. Do not over- tighten the screws to prevent damage to the Loop Power enclosure.

For best performance the batteries should be replaced as soon as the low battery indication is noticed (flashing status LED while connected).

Block Diagram

Figure 1: Block Diagram

Connecting to a Loop Device

Loop Power is a fully contained power source for 4-20 mA loop powered transmitters. Internal batteries eliminate the need for external connections to AC power or USB ports as a power source while providing complete galvanic isolation.

Connect the red clip to power or loop (+) and the black lead to power or loop (-) on your transmitter. See Figure 2 Device Connections for details. The transmitter can be powered with or without the milliamp meter connected. The power loop is not opened when the meter is removed or not attached.

With power clips a ached to the transmitter, press the Loop Power connect bu on to enable power to the transmitter. The status LED will be ON while the power output is active. If the LED is not ON solid while active, refer to Status LED Operation in this manual.

To remove power from the transmitter press the connect bu on. The LED will be OFF while the supply output is inactive.

The Loop Power includes a 250 ohm loop resistor that will drop a por on of the available 24 volts. The voltage dropped across the resistor depends on the current requirements for the loop transmitter. Open circuit voltage, with no transmitter a ached, is 24 volts +/- 2%.

Measuring Loop Current

Loop Power includes leads to simplify connection to a DC current meter for loop current measurements. The current meter leads have safety insulated banana plugs that can be plugged directly into a standard current meter. An internal diode allows the meter to be connected or disconnected without interrupting the loop supply or opening the loop. See Figure 2 Device Connections for details.

HART Protocol Modem Connections

A HART modem or HART communicator can be connected to Loop Power using the two clip-terminals provided next to the current meter leads. The clip terminals allow standard HART modem mini-clips to be easily connected across an internal 250 ohm loop resistor.

Figure 2: Device connections

Milliamp Meter (optional)

1 Connect a milliamp meter to the shielded banana jack leads to monitor loop current.
Removing the current meter does not open the loop.

Loop Transmitter

2 Connect the red mini-clip to the transmitter (+) supply terminal.
Connect the black mini-clip to the transmitter (-) supply terminal.

3 For calibrating HART devices a HART protocol modem or calibrator can be attached across the internal 250 loop resistor by clipping on as shown.

Status LED Operation

The Status LED provides quick feedback of the Loop Supply operating mode. The LED can indicate when the battery is getting low and needs to be replaced or when the output is shorted or connected to a load that exceeds the 30 milliamp maximum.

LED Off
If the status LED is off, the Loop Power is not supplying power to the output. If the LED remains off a er the bu on is pressed, the internal batteries need to be replaced. For details refer to the sec on on “Replacing Batteries” in this manual.

LED On
When Loop Power is active and providing power to the output, and no fault conditions are detected, the LED will be ON solid.

LED Fast Flash then Off
If an over-current condition is detected, more than 30mA or shorted, the output will be disconnected and the led will flash for about 2 seconds. Remove the overload or shorted condition and press the connect bu on to restore the active output.

LED Slow Flash
A slow flashing status LED indicates that the output is connected but the internal supply is low and the batteries need to be replaced. The power output may not be fully regulated when the batteries are low. Replace the internal three “AAA” alkaline batteries if they are low to ensure a stable power output. For details refer to “Replacing Batteries” in this manual.

Auto Power Off

To help reserve battery life Loop Power will automatically disconnect and power down a er 30 minutes. Press the connect bu on to re-connect.

Specifications

Output

Open Loop Voltage …………………………. 24V +/- 2%
Load Regulation ………………………………. 0.25%
Noise ………………………………………………. Less than 50mV P-P @ 20mA
Current ……………………………………………. 30mA max
Short Circuit / Overload Protection …….. Auto-disconnect if load is > 30mA
Leads ……………………………….. 3′ (1 meter) high flexibility test lead wire
Termination ……………………… Mini-Grabber clips

Current Meter Leads

Leads ……………………. 2 Feet (0.6 Meter) high flexibility test lead wire
Termination ………….. Shielded banana plugs, Red (+), Black (-)

HART Protocol Support

Connection Type ………………. clip loop terminals (.087″ x .055″ hole)
250Ω Loop Resistor …………….. Included internally

Battery

Type ………………………………………………….. 3 x 1.5V “AAA” alkaline
Operating Life ……………………………………. > 6 hours with 12mA load
Battery Supply Range (DO NOT USE 3V CELLS) …. 2.0V to 5.5V
Low Battery Indicator …….. Status LED will flash slow while output is active
Low Battery Level …………… 2.49V
Auto Off duration …………… 30 minutes

Enclosure

Molded ABS Plastic
Weight (including leads and batteries) ……………. 6 ounces
Enclosure Dimensions …………………………………… 1.70″ x 3.25″ x 1.13″

Environmental

Operating Temperature …………………… -30ºC to 50ºC (-22ºF to 122ºF)
Storage Temperature ………………………. -40ºC to 70ºC (-40ºF to 158ºF)
Humidity …………………………………………. 0 to 95% (non-condensing)

Dimensions

Figure 3: Dimensions

Limited Warranty

Microflex, LLC warrants this unit against defects in materials and workmanship for a period of one year from the date of shipment. Microflex, LLC will, at its op on, repair or replace equipment that proves to be defective during the warranty period. This warranty includes parts and labor.

A Return Authorization (RA) number must be obtained from the factory and clearly marked on the outside of the package before equipment will be accepted for warranty work.

Microflex, LLC believes that the information in this manual is accurate. In the event that a typographical or technical error exist, Microflex, LLC reserves the right to make changes without prior notice to holders of this edition. The reader should consult Microflex, LLC if any errors are suspected. In no event should Microflex be liable for any damages arising out of or related to this document or the information contained in it.

EXCEPT AS SPECIFIED HEREIN, MICROFLEX, LLC MAKES NO WARRANTIES OR MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. CUSTOMER’S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF MICROFLEX, LLC SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER. MICROFLEX, LLC WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA, PROFITS, USE OF PRODUCTS, OR INCIDENTAL OR CONSEQUENTIAL DAMAGES, EVEN IF ADVISED OF THE POSSIBILITIES THEREOF. This limitation of the liability of Microflex will apply regardless of the form of ac on, whether in contract or tort, including negligence. Any ac on against Microflex, LLC must be brought within one year a er the cause of ac on accrues. The warranty provided herein does not cover damages, defects, malfunctions, or service failures caused by owners failure to follow Microflex’s installation, opera on, or maintenance instructions; owners modification of the product; owner’s abuse, misuse, or negligent acts; and power failure or surges, fire, flood, accident, actions of third parties, or other events outside reasonable control.

Microflex, LLC
35900 Royal Road            Phone 281-855-9639
Pattison, Texas 77423      Fax 832-422-4391
USA                                www.microflx.com

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