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        991-25-50-01-01

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        1001 reviews ｜ Need a Specific Revision?
        The Bently Nevada 991 Vibration Transmitter 991-25-50-01-01, is a versatile device that converts vibration signals from proximity probes into a standard 4-20 mA process signal.
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        Warranty Policy
        We provide 1 year warranty for all remaining parts.
        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
        Return Notice
        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
        In the event of a defect, we will send new equipment, repair equipment or refund the purchase price based on our availability. You must contact us to obtain a return authorization and return the defective device to us within 14 days of reporting the defect.
        Shipping Mode
        Various transportation options are available in each country. Shipping methods and fees are clearly indicated on all quotations.Various transportation options are available in each country. Shipping methods and fees are clearly indicated on all quotations.
        Parts Availability
        Apter Power offers a wide range of components, products and services related to industrial automation. We also supply new products from a variety of quality manufacturers.
        How to order
        We have been working hard to update our inventory. If we have stock or parts available for new factory purchases, you can contact the order online. If we do not currently have an inventory, the displayed quantity will show "Ask". Please create an online quote or contact us by phone, fax or email to check availability.

        Technical specifications for 991-25-50-01-01

        • Manufacturer:
          Bently Nevada
        • Part Number:
          991-25-50-01-01
        • Product Family:
          991 Thrust Transmitter
        • Full-scale:
          25-0-25 mils
        • System Length:
          5.0 meters (16.4 feet)
        • Mounting:
          35 mm DIN-rail clips
        • Agency Approval:
          CSA Division 2
        • Test Adapter Function:
          Provides Isolation, Signal Inversion, and Conditioning
        • Primary Purpose:
          Continuous Machinery Protection (4-20 mA) + Advanced Diagnostic Capability (PROX OUT)
        • Weight:
          0.44 kg
        • Estimated shipping dimensions:
          10x7.3x6cm
        • Tariff Code:
          8537101190
        • Country of origin:
          USA
        • Place of shipment:
          Xiamen, Fujian, China
        By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.
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        Description
        A key component in predictive maintenance strategies is the 991-25-50-01-01 Vibration Transmitter, which serves a dual purpose in machinery monitoring. Its primary function is to condition the signal from an eddy current proximity probe and transmit a scaled, robust 4-20 mA output representing vibration levels to a Distributed Control System (DCS) or PLC for continuous protection and trending. 

        However, a crucial safety and signal integrity consideration for the 991-25-50-01-01 is that the PROX OUT signal is not electrically isolated from the 4-20 mA loop power. While it can be connected directly to battery-powered or internally isolated portable data collectors, connecting it to AC-powered bench test equipment like oscilloscopes or spectrum analyzers without proper isolation poses a risk of ground loops, potential damage to equipment, and compromise of the machinery protection loop. 

        The recommended solution for safe and compliant diagnostics is the 990/991 Test Adapter. This dedicated accessory is specifically designed to interface with transmitters like the 991-25-50-01-01. It performs several essential functions: it provides full galvanic isolation between the transmitter's PROX OUT circuit and the test equipment, it inverts the signal to preserve the industry-standard convention for vibration signal polarity (so that a positive voltage corresponds to a gap decrease), and it conditions the signal to appropriate levels for standard test instruments.

        Implementing the 991 Transmitter and its test adapter as a system represents best practice in machinery monitoring. The 991-25-50-01-01 handles the continuous protection and basic monitoring duty, while the PROX OUT path, when accessed via the test adapter, opens a window for advanced diagnostics without downtime.
        Alternative Names
        991-06-50-01-01 991-25-70-01-01 991-25-50-02-01 991-25-50-03-05
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        FAQS

        The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
        VIEW ALL FAQS
        Can I connect my oscilloscope directly to the PROX OUT port on my 991-25-50-01-01 transmitter for diagnostics?
        No, this is not recommended and can be unsafe for standard AC-powered oscilloscopes. The PROX OUT signal on the 991-25-50-01-01 is explicitly not isolated from the transmitter's 4-20 mA loop. Direct connection risks creating ground loops, damaging your oscilloscope or the transmitter, and compromising the integrity of the protection signal. You must use the 990/991 Test Adapter to provide the necessary isolation and signal conditioning for safe use with bench equipment.
        What is the purpose of the 990/991 Test Adapter when using the 991-25-50-01-01?
        The 990/991 Test Adapter is a critical interface device designed specifically for transmitters like the 991-25-50-01-01. It serves three key functions when used with the PROX OUT port: 1) It provides galvanic isolation between the transmitter and the test equipment, protecting both. 2) It inverts the signal to maintain the industry-standard polarity convention for vibration analysis. 3) It conditions the signal to be compatible with the input requirements of typical AC-powered diagnostic equipment such as spectrum analyzers and oscilloscopes.
        Under what conditions can I connect equipment directly to the PROX OUT of my 991-25-50-01-01 without the test adapter?
        Direct connection to the PROX OUT of a 991-25-50-01-01 is only permissible if the test equipment is itself battery-powered and has isolated inputs. Many modern portable vibration data collectors fall into this category. The key requirement is that the diagnostic device does not introduce a ground path back to the AC mains that could conflict with the transmitter's ground, as the PROX OUT circuit is non-isolated.
        Why is signal isolation so important when using the diagnostic feature of the 991-25-50-01-01 transmitter?
        Isolation is paramount for two main reasons when accessing the PROX OUT of the 991-25-50-01-01. First, for Safety and Equipment Protection: Without isolation, connecting AC-powered test gear can create a ground loop through the transmitter's 4-20 mA loop, potentially leading to large circulating currents that can damage sensitive electronics. Second, for Machinery Protection Integrity: Any fault or noise introduced via the diagnostic connection could potentially affect the primary 4-20 mA output, which is the vital signal used for machinery alarm and shutdown protection. The 990/991 Test Adapter eliminates this risk.

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