Wilcom MODEL T336B CIRCUIT TEST SET Operating Instructions
T336B Circuit Test Set Operating Instructions 810-311-007 June 2005 Copyright (c) 2005 Wilcom All Rights reserved Wilcom reserves the right to make changes to the material contained herein without notice and shall not be liable for errors contained herein or for incidental, consequential damage in connection with the furnishing, performance or use of this material. This document may not be copied or duplicated in part or in whole for any purpose without the express written permission of Wilcom.
Contents Introduction... 1 Panel Controls and Connections... 3 Operation... 6 General Procedure... 6 Circuit Measurement Procedures... 6 Application Notes... 9 Performance Limits... 9 Measurements at the Subscriber Location... 9 Measurements at the Central Office Location.. 9 Balance Measurements... Specifications... Maintenance... Battery Replacement... Service & Repair... Warranty... 11 12 17 17 18 20 Figures 1. T336B Front Panel... 2. Current Measurement Plot... 2 8 ii
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Introduction The Model T336B Circuit Test Set is a portable, compact, combination level and noise measuring set. It is the functional equivalent to the Wilcom T136 series of test sets, but a 3-1/2 digit LCD display replaces the analog meter. The T336B also has provisions for measuring DC resistance and voltage. Powered by two 9-volt batteries, the T336B is designed to make circuit level and noise measurements over a wide range of applications. When circuit loss, noise metallic or noise to ground are displayed, a visual indication is given if the displayed reading is over or under the accuracy range of the RMS to DC converter, the T336B measures DC volts from ring to tip lead and current from the ring lead to ground. This measurement allows evaluation of station integrity. Since the office battery potential, loop length, station ground resistance, and other variables affect the magnitude of current to ground, exact ground resistance is difficult to determine. The data pads that are used with the T336B include a table to facilitate determining if the station ground is at fault. Circuit connection is accomplished by using three 5 ft. long leads colored Green for tip, Red for ring, and Yellow for ground. These leads are permanently connected to the T336B and have universal test clips to facilitate circuit connection. 1
Features Wilcom MODEL T336B CIRCUIT TEST SET LO BAT 1.8 8.8... CONNECT GROUND LEAD FIRST GRN-T RED-R YEL-GND PUSH TO MEAS KILOHMS dc OHMS dc DIAL & dc VOLTS GND ma LOOP ma CKT LOSS dbm CKT NOISE dbrnc PWR INFL dbrnc DIAL & MONITOR Figure 1. T336B Front Panel 2
Panel Controls and Connections The following describes the function and operation of the T336B panel controls, connections, and indicators (see Figure 1 on opposite page). The 3 1/2 digit LCD Display indicates measurements from -199.9 to +199.9. A low battery indicator (LO BAT) is located in the upper left corner. Negative readings are indicated by a minus sign that precedes the reading; positive numbers are indicated with no sign. A fixed decimal allows display accuracy at one-tenth of a unit. The PUSH TO MEAS Switch enables display of the measured level for a period of 60 seconds. The T336B circuits are activated only when you press the PUSH TO MEAS button. The PUSH TO MEAS switch has to be operated for DC current measurement. Polarity is indicated which eliminates the need for a polarity bridge. The Function Switch is an 8-position rotary switch that is used to select the desired measurement: 1. OHMS DC allows measurement of 0 to 1999 Ω using the tip (green lead) and the ring (red lead). 2. KILOHMS DC is the same as OHMS DC but with a range of 0 to 1999 kω. 3
Panel Controls and Connections 3.GND ma indicates the DC current drawn by a resistance of approximately 430 Ω connected between the ring lead and the station ground. A positive reading is indicated with negative battery connected to the ring lead. 4. DIAL & DC VOLTS allows connection of a headset to the line for dialing purposes. The DC VOLTS measures the typical line voltage on tip and ring at an impedance of approximately one MΩ. The DC voltage range is 0 to ±199.9V. A positive reading is indicated with negative battery connected to the ring lead. Please note that the maximum voltage rating from tip to ring is 96V AC or dc. The maximum rating from tip or ring to ground is 500V DC or 250V AC. 5. LOOP ma (dc loop current) indicates the DC current that is drawn by a DC resistance of 430ý connected across tip-to-ring. A positive reading is indicated with negative battery connected to the ring lead. 6. CKT LOSS (transmission) measurements can be taken over a level range of -55 to +5 dbm. The signal level received is terminated and the level is read directly from the LCD display. Measurements may be made at frequencies other that 1 khz as the CKT LOSS response characteristic is flat from 200 to 4000 Hz; 60 Hz is attenuated down 25 db. 4
Panel Controls and Connections 7. CKT NOISE (noise metallic) is measured on a C- Message weighted basis. Noise level readings on the display vary at a greater rate than those on an analog meter as it has no mechanical damping effect. The display is updated two or three times per second for noise fluctuations. 8. PWR INFL (noise-to-ground) is measured between a circuit and ground on a C-Message weighted basis. The input circuit in this position has an impedance greater than 10 MΩ dc; tip and ring are taken together to ground. The PWR INFL display is calibrated to read the noise to ground directly in dbrnc (600 Ω voltage equivalent). Dial and Monitor Connections from the front panel provide convenient locations for connecting a handset/ headset. Connections to the circuit to be tested are made with the universal clips on the 5 ft. long leads. The leads are color coded green for tip, red for ring and yellow for ground and are also marked T for tip, R for ring, and G for ground. These leads are permanently attached to the set. 5
Operation The following describes general operating instructions for the T336B. Also described are the procedures that you can use to make circuit measurements. General Procedure 1. Connect the test leads to the circuit under test using the green lead for tip, the red lead for ring and the yellow lead for ground. CAUTION: GROUND should be connected first. 2. Connect a handset/headset to the DIAL & MONI- TOR posts or jack. Set the function switch to DIAL & DC VOLTS. When you hear a dial tone you can then call the desired number. 3. Press the PUSH TO MEAS button each time you wish to make a measurement. Circuit Measurement Procedures OHMS DC: Circuit continuity and resistance may be checked in this position. Resistance measurements can be displayed from 0 to 1999 Ω. Refer to Specifications for display accuracy. Use the tip (green) and ring (red) leads for resistance measurements. KILOHMS DC: This function is the same as OHMS DC above but with a measurement range of 0 to 1999 kω. 6
Operation GND ma: This measurement is useful for evaluating station grounds. Plot this measurement on the reverse side of the Wilcom Data Reporting Pad as I (G)mA. The second measurement is LOOP ma or I(L)mA. ( See Figure 2 ) DIAL & DC VOLTS: Use this position when calling a number. Then check the line voltage after the called number answers. LOOP ma: This measurement, along with the GND ma measurement, is plotted on the reverse side of the Wilcom Data Reporting Pad. The intersection of the two points indicates the condition of station ground. CKT LOSS dbm: Dial the milliwatt generator at the central office. When the tone is received measure the level. Knowing the output level of the generator and the measured level, the circuit loss can be determined (e.g. generator output level equals 0 dbm, measured level equals -15 dbm, therefore, the CKT LOSS equals 15 db). CKT NOISE dbrnc: Dial the quiet (or balanced) termination at the central office. When the termination is received measure the noise metallic. PWR INFL dbrnc: Establish connection to a quiet (or balanced) termination. Noise to ground can now be measured. The reading is displayed directly in dbrnc, (600 Ωvoltage equivalent). 7
Operation Note: This chart shows acceptable readings above the curved line and unacceptable readings below the curved line. By plotting the loop current I(L)mA and the ground current I(G)mA it is possible to determine if the station ground is aceptable or not. Where the two readings intersect is the point of acceptability or unacceptability. To use the chart, first measure and plot the loop current I(L)mA, then measure and plot the ground current I(G)mA. For example; if the loop current is 35ma and the ground current is 60ma, an adequate station ground exists.if the intersection of the two measuremtns fall below the curved line then the station ground and bond should be checked. Figure 2 Current Measurement Plot 8
Application Notes The following describes use of the T336B in taking noise measurements at the subscriber and central office locations, and examining circuit balance. Performance Limits The measurement ranges of the T336B are designed to be within the normally acceptable limits of circuit loss, circuit noise (noise metallic) and power influence (noise to ground). Should the measured reading exceed the accuracy range of the built-in RMS to DC converter, the unused decimals and colon flash on the display. Measurements at the Subscriber Location Measurements may be made from the terminal block or protector block at the customer's location. It is not necessary to disconnect the customer's equipment, but the equipment must be in the ON HOOK condition when making measurements. The leads on the T336B are connected to the circuit using the green lead for tip, the red lead for ring and the yellow lead for ground. A good ground, preferably the ground at the protector block, must be available to make power influence measurements. Measurements at the Central Office Mainframe Noise measurements may be made at the main frame in a C.O. toward the subscriber or toward the office equipment. 9
Application Notes Toward Subscriber. Meaningful noise measurements can only be made toward the subscriber when there is a termination at the far end. If a section of the subscribers loop is to be measured, a termination should be connected at the far end of the section. A Wilcom Model T279 Circuit Termination Set is useful in providing such a termination. Unterminated measurements do not provide useful data for analyzing noise problems. However, if a large number of unterminated loops are tested, useful statistical information can be compiled on the extent of noise on loops out of a central office. Please note that heat coils should be removed during testing. To Central Office Equipment. To determine the level of noise that originates in the central office and the balance of the office equipment, remove the heat coils and connect the tip and ring leads to the terminals of the office equipment. Connect the ground lead to C.O. ground bus and dial the quiet termination to make CKT NOISE and PWR INFL measurements. If the induced longitudinal voltage is low, it may not be possible to make noise measurements. It is then necessary to introduce an external longitudinal voltage at a fixed frequency; any signal source between 500 and 1000 Hz is satisfactory. A Wilcom Model T137B is useful for providing a balanced terminating circuit to which a longitudinal voltage source can be connected. 10
Application Notes Balance Measurements Circuit balance can be determined from the CKT NOISE and PWR INFL measurements made with the T336B by using the following formula: Balance (db) = PWR INFL (dbrnc) - CKT NOISE (dbrnc) The balance of a circuit determines how sensitive it is to the induction of noise. The following values provide a guide for determining acceptable balance: Balance Condition Over 60 db Excellent 50-60 db Good 40-50 db Fair Under 40 db Poor Typically, any balance under 50 db requires improvement, particularly when the power influence is high, i.e., over 75 dbrnc as measured on the T336B. If power influence is low, a greater degree of imbalance can be tolerated. However, if the power influence should increase, the practice is to get as high a balance as possible. 11
Specifications Manufacturer Models Name Operational Ranges OHMS DC: KILOHMS DC: GND ma: dc VOLTS: LOOP ma: CKT LOSS: CKT NOISE: PWR INFL: Wilcom T336B Circuit Test Set 0 to 1999 Ω, 1Ω resolution 0 to 1999 kω, 1kΩ resolution 0 to ±199.9 ma DC (0.1 ma resolution) in 430 Ω 0 to +199.9V DC (0.1V resolution), across 1 mω resistance 0 to ±199.9 ma DC (0.1 ma resolution) in 430 Ω -55 to +5 dbm, 0.1 db resolution in 600 Ω 0 to 60 dbrnc in 600 Ω, 0.1 db resolution 50 to 110 dbrnc, 0.1 db resolution 12
Specifications Accuracy (@ 25 C): OHMS DC: 400 to 1000 Ω ; ±1% Other readings: ±2% + 2Ω KILOHMS DC: ±3% + 2 kω dc Volts: ±2% + 0.2V GND ma at 20 ma: ±0.2 ma Other readings: ±2% + 0.2 ma LOOP ma at 20 ma: ±0.2 ma Other readings: ±2% + 0.2 ma CKT LOSS (w/ 1004 Hz tone): CKT NOISE (w/ 1004 Hz tone): PWR INFL: ±0.1 db from -10 to 0 dbm ±0.2 db from -40 to +5 dbm ±0.3 db from -55 to -40 dbm ±0.3 db at 30 dbrnc ±0.5 db from 20 to 60 dbrnc ±1.0 db from 0 to 20 dbrnc ±0.5 db from 70 to 110 dbrnc ±1.0 db from 50 to 70 dbrnc 13
Specifications Change w/ temp relative to 25ºC: dc measurements: ±1% max, -20º to 50ºC LOSS and NOISE measurements: ±0.2 db max. at 0º to 50ºC ±0.5 db max. at -20ºC Frequency Response CKT LOSS: 4 khz: Flat within accuracy specs 200 Hz to 400 Hz: ±0.5 db relative to 1004 Hz 4 khz to 15 khz: ±0.5 db relative to 1004 Hz 60 Hz down at least 20 db relative to 1004 Hz CKT NOISE: PWR INFLUENCE: Input Impedance OHMS DC: C-Message Weighting C-Message Weighting High resistance 1 ma current source KILOHMS DC: High resistance 1µA current source GND ma: 430Ω ±1% DC ring-to-ground; tip open-circuit 14
DIAL & DC VOLTS: Specifications Tip and Ring directly connected to DIAL & MONITOR terminals, 1 MΩ shunt Other FUNCTION Positions: Tip-to-Ring: Return loss: Tip-Ring to GND: Miscellaneous Monitor Output: Push to Measure: Detector: 430Ω ±1% dc, 600Ω ac >30 db with respect to 600 Ω 200 Hz to 15 khz >10 MΩ dc, >100 kω AC Balanced 600 Ω output, approx. 0.25V at center of each autorange. At DIAL & MONITOR terminals during CKT LOSS, CKT NOISE, and PWR INFL measurement. Push button ON Auto-off after approx. 60 sec. True rms Longitudinal Balance: >100 db at 100 Hz, decreasing 20 db/decade at higher freq. Digital Readout Response: Approx. 1 second for 10 db level change. Two or three updates/ second for noise fluctuations. 15
Specifications Tip or Ring to GND: Maximum Ratings Tip-to-Ring: Power Batteries: DC: 500V, AC: 250V AC to DC, 96V applied through 400 Ω Two 9V NEDA 1604 or1604a Battery Life: 30 hours continuous, or 1800 operations of the PUSH TO MEAS switch. Environmental Operating: Operating Temp.: Humidity: Altitude: Storage Temp.: -20 to +50 C 90% at 35 C, 40% @50 C to 5000 meters -50 to +70 C Physical Width: 4-3/8 in. (11.0 cm) Height: 6-3/8 in. (16.0 cm) Depth: 4-7/8 in. (12.5 cm) Weight: 2.9 lbs. (1.3 kg) 16
Maintenance Battery Replacement To replace the two 9-volt batteries, remove the unit from the case by loosening the four screws that are indicated with arrows on the panel (Figure 1). The batteries can then be easily replaced. CAUTION: To prevent possible circuit malfunction, power off the unit before removing the batteries. 17
Service and Repair For service or repair follow the procedure below: 1. Call Wilcom Customer Service. Support personnel will determine if the equipment requires service, repair or calibration. 2. If the equipment must be returned to Wilcom for service, Wilcom Customer Service will issue a Return Material Authorization (RMA) number and the following address for return: Wilcom 73 Daniel Webster Highway Belmont, NH 03220 TEL (800) 222-1898 (USA only) or (603) 524-2622 FAX (603) 524-3735 www.wilcominc.com IMPORTANT Never send any equipment back to Wilcom without a Return Material Authorization (RMA) number. 3. Pack the equipment in its original shipping material. Be sure to include a statement or report fully detailing the defect and conditions under which it was observed. 18
Service and Repair Also be sure to include a contact name and telephone number. 4. Return the equipment, prepaid, to the above address. Be sure to write the RMA on the shipping slip. Wilcom will refuse and return any package that does not bear the RMA. Ordering Information Orders for any of the Wilcom products and any of their optional accessories should be directed to the address shown above. 19
WARRANTY All products are warranted against defects in materials and workmanship. This warranty applies for a period of two (2) years from date of delivery, except for Fiber Optic instrumentation and equipment which have a one (1) year warranty on parts and two (2) years on labor. (The only exception in the digital testing equipment is the D550 Shark, which has a warranty of one (1) year from date of delivery.) Wilcom's obligation under this warranty is limited to servicing or adjusting each instrument returned to its factory within the warranty period, and to replace any components found to be defective. If determined that the defective condition is a result of misuse or abnormal operation, repairs will be billed. LIMITATION OF WARRANTY The foregoing warranties are the exclusive warranties provided by Wilcom. Wilcom will not be liable for any special, indirect, incidental or consequential damages whatsoever resulting from loss of use, loss of data or loss of profits arising out of or in connection with the use or performance of the product, even if Wilcom has been informed of the possibility of such damages in advance. All implied warranties, including without limitation warranties of merchantability and fitness for a particular purpose, as well as warranties arising from a course of dealing or usage of trade are expressly disclaimed. PROPRIETARY INFORMATION The information contained in this manual is the proprietary material of Wilcom, and may not be reproduced, used for manufacturing purposes, or disclosed to others 20