H Heuer Instruments UMDT51A User Manual Download Page 65

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Making Measurements

LT51 User Manual

AC Impedance (MAGZ)

Measure the

magnitude

of the AC impedance between the RTXa-b connector

terminals in



. The internal bridge network with a reference of 75



, is always

used to measure the impedance, and provides adequate accuracy for all
frequencies from 1 kHz to 500 kHz:



press the key and then [f4] to select Mag (Z)





press the key to see a plot of the impedance over the frequency span.

Summary of Contents for UMDT51A

Page 1: ...A LINE TESTER LT51 200 Hz 2 2 MHz H HEUER INSTRUMENTS PTY LTD 766 Pennant Hills Road Carlingford NSW 2118 Sydney Australia Web www heuer com au Tel 61 2 9871 8207 Fax 61 2 9872 5985 Rev 9 1 April 2021...

Page 2: ...gation is limited at H Heuer Instruments option to refund of the purchase price free of charge repair or replacement of a defective product which is returned to H Heuer Instruments within the warranty...

Page 3: ...arth of any RTX a b g terminal is 60 V dc 30 V rms 42 V peak and either TX a b terminal is 60 V dc Never connect the LT51 to an outdoor circuit during lightning storms Disconnect all external cables b...

Page 4: ...are used in this guide DANGER Risk of electric shock ATTENTION Refer to Manual Equipment is protected by reinforced insulation to protect the user against electric shock Functional Earth Ground Termin...

Page 5: ...Use Alkaline cells only when the NiMH cells are discharged and the AC adaptor is not available Always replace Alkaline cells with NiMH when available Remove NiMH batteries if the LT51 is going to be s...

Page 6: ...is approximately 6 hours for 2100mAh cells When the battery is charging the Red charging LED illuminates When charging is complete the Red LED goes off and the Green DC LED will illuminate WARNING Do...

Page 7: ...stralia 61 2 9871 8207 Visit our website for the latest list of phone numbers If the LT51 requires repair service centre personnel will provide you with shipping information and repair prices If the L...

Page 8: ...stralia Declare under our own responsibility that Product Name LT51 Line Tester Product Type Test and Measurement Equipment to which this declaration refers conforms with the following relevant standa...

Page 9: ...escription 1 2 Controls and connections 3 Welcome screen 4 LCD 5 Keypad 6 Test lead connectors 8 Balanced Interfaces 8 Unbalanced Interfaces 8 USB port 9 DC power jack 9 Microphone and speaker 9 Knob...

Page 10: ...1 Frequency Bandwidth 31 Frequency span 31 Centre Frequency Selective Level Meter 31 Bandwidth Selective Level Meter 32 AFC Automatic Frequency Control 32 Averaging Peak Hold 32 POTS Connection 33 Goi...

Page 11: ...Factor 60 Cable 61 Pulse width 62 Adjusting the TDR display 62 Cursor 62 Vertical zoom 62 Horizontal zoom 63 Horizontal offset 63 Vertical offset 63 Peak Events 64 Dip Events 65 Blind spot 65 Saving m...

Page 12: ...EXT Near End CossTalk 84 DC Voltage Measurement 85 AC Voltage Measurement 85 AC Impedance Measurement 85 10 Specifications 87 Physical 87 Power supply 87 Interfaces 87 Standards compliance 87 Regulato...

Page 13: ...orrosion and X Talk are easily located with the LT51 Great care has been taken to achieve easy operation of this instrument Most functions are accessed by a single button press or one further soft key...

Page 14: ...l or Numerical measurement display Marker functions for navigating graphical displays using cursor Remote control of LT51 by PC via serial port over opto isolated USB link Easy test result storage and...

Page 15: ...Controls and connections LT51 User Manual 3 2 Controls and connections Figure 2 1 LT51 front panel Knob Microphone Measurement keys Configuration keys Soft keys Speaker On Off key LEDs LCD...

Page 16: ...lear the LT51 tester has a problem An incompatible version of firmware for the LT51 hardware will cause the screen to hang and display an error message Obtain the correct version of the firmware and d...

Page 17: ...y level and Ztx Results displays the test results in DMM graphical format or as lists The current marker position and value are displayed during graphical displays The active RTX terminals filter and...

Page 18: ...t Loss Causes the LT51 to go off hook on the RTXa b test leads and function as a telephone dial set Hangs up returns to on hook when this key is pressed again Perform a TDR measurement on the pair con...

Page 19: ...ed directly beside the LCD These are software defined keys called soft keys that carry out commands related to the currently displayed screen To locate the function of a key look on the LCD directly b...

Page 20: ...lance or RFL measurements only not available in this model TX a black and b red The LT51 output TX signals appear at the TXa b terminals See RTX terminal description above when the LT51 is configured...

Page 21: ...lt in microphone and speaker is provided for voice conversation when the LT51 is acting as a telephone Line activity and tone reception on the RTXa b terminals can also be monitored with the speaker K...

Page 22: ...ncy it is possible to set the value using the knob or directly via the keypad Once the first digit is entered via the keypad a selection of units appears in the menu next to the soft keys When the des...

Page 23: ...Term The LT51 RTX input impedance is now 600 terminated 4 Press the key followed by the f1 soft key to set the frequency Span Use the knob to set the span to 4 5 kHz 5 Press the f3 soft key to set BW...

Page 24: ...ed by the f4 soft key to set the TX Freq to 1000 Hz using the Knob or Keypad and press the button to clear the Dialog box or appropriate fx soft key if using keypad 6 Press the f2 soft key to set the...

Page 25: ...Keypad and press the button to clear the Dialog box or appropriate fx soft key if using keypad 6 Press the key followed the f4 soft key to set the Zero Offset for the level measured at 1000 Hz 7 Press...

Page 26: ...Keypad and press the button to clear the Dialog box or appropriate fx soft key if using keypad 5 Press the key followed by the f1 soft key to set the frequency Span Use the knob to set the span to 4 5...

Page 27: ...OPH to make psophometric weighted measurements 6 Press the key followed by the f3 soft key to set the TX Source to SINE Press the f4 soft key to set the TX Freq to 1014 Hz using the Knob or Keypad and...

Page 28: ...ed measurements 6 Press the key followed the f3 soft key to set the Source to G227 TEL to transmit the 0 dBm Telephone Noise signal on the TXab terminals 7 The display will show the received level and...

Page 29: ...Freq 10 kHz Mode TX RX 4W 3 Press the f2 soft key to select the Voltage DC AC measurement 4 The DC voltage of the line is displayed 5 Apply ring signal to the RTXab terminals of the LT51 6 You will he...

Page 30: ...e and current through the 600 termination is displayed 5 If connected to the PSTN dial DTMF digits using the keypad to make a connection 6 While TX displays TALK use the hands free telephone to transm...

Page 31: ...system unit 2 Press the key followed by the f2 Meas Settings soft key Press the f2 Reset LT51 soft key 3 Press the button then the f1 soft key to set ZRTX to 75 HiZ 4 Press f3 RxRange soft key and tu...

Page 32: ...the TXa b outputs Set the desired TX level using the Knob or Keypad and press the button to clear the Dialog box or appropriate fx soft key if using keypad Press the f4 soft key to set the TX Frequenc...

Page 33: ...nuator Example Measurement results for 3 frequencies Frequency Hz Theoretical level Measured levels with 40 dB attenuator Tx pilot 499820 26 dBm 14 00 40 26 dBm Rx pilot 500180 0 2 dBm 40 00 40 0 dBm...

Page 34: ...Testing PLC Systems LT51 User Manual 22...

Page 35: ...he button then the f1 soft key to set ZRTX to 75 to make the return loss measurement against a 75 reference 6 Press the key followed by the f4 soft key to set the desired TX Frequency using the Knob o...

Page 36: ...cy by pressing the key followed by the f4 TX Freq soft key Use the Knob or Keypad and then press the button to clear the Dialog box or appropriate fx soft key if using keypad OR Press the key to show...

Page 37: ...structures Following are the LT51 configuration keys Configure the LT51 receiver parameters at the RTXa b terminals such as Zrtx terminated HiZ range setting and RTX 2 Wire or TX RX 4 Wire interface C...

Page 38: ...E When the transmitter interface is set to RTX any change in the output impedance is reflected back to the input impedance and vice versa Transmit source It is possible to mute the TX output and simul...

Page 39: ...solution Repeat this process to a resolution of 1 Hz or until the desired frequency is obtained Press the key or any key to clear the dialog box The current setting for TX frequency only if Source is...

Page 40: ...as Settings then f4 Sweep Step to show the possible settings for the Sweep Step parameter The Sweeping Step parameter controls the step size between successive sweep frequencies The parameter can be s...

Page 41: ...ged except in the off hook condition when it is terminated to sink loop current and hold the loop see POTS section a special hybrid is used to ensure the selected AC impedance is provided for making P...

Page 42: ...isabled although the setting is not changed during AutoTest mode when sweeping is active when connected to a slave LT51 If any filter is set If the centre frequency is 0 Hz Interface The transmitter c...

Page 43: ...he LT51 Transmitter is ON sourcing a tone eg Return Loss NEXT Loss Balance etc the span will be automatically set to receive the current Transmit Frequency This does not apply when making selective me...

Page 44: ...urrent setting for BW is displayed below the frequency axis or under the frequency result in DMM mode AFC Automatic Frequency Control Press the key and then toggle f4 to set AFC ON or OFF With a centr...

Page 45: ...pedance is terminated to sink loop current and thereby seize the line To ensure the correct AC impedance is presented at the RTX terminals a special hybrid circuit is deployed providing accurate TX le...

Page 46: ...igits stored in the Redial buffer To view the contents of the Redial Buffer on the LCD press the f2 key Speaker Phone The Hands free Speaker Phone becomes active indicated by Tx Talk in the TxStatus b...

Page 47: ...ak The marker moves to the location of the next peak value on the waveform either left or right of the current marker position that is lower than the current marker value Zero offset Press the f4 key...

Page 48: ...key followed by the f3 LT51 Settings soft key Press the f5 Contrast soft key Turn the knob clockwise to increase or anti clockwise to reduce the contrast of the LCD This value is permanently stored i...

Page 49: ...press the f1 Date soft key Enter the current date using the keypad digits Pressing the key will advance the cursor to the next digit When the date is correct press any non digit key to exit To modify...

Page 50: ......

Page 51: ...ting Softkeys allow selection of various measurements such as Level Noise DCV ACV Return Loss Impedance Next Loss Causes the LT51 to go off hook on the RTXa b test leads and function as a telephone di...

Page 52: ...then f1 twice to select Level Noise The RMS value is the total signal power across the frequency span The following settings are relevant to Level Noise measurements and should be set according to req...

Page 53: ...following example where there are two tones close to 1 000 kHz illustrates this feature Examining the spectrum from baseband with a span of 1 200 kHz it is clear there are two peaks close to 1 000 kH...

Page 54: ...alue displayed represents the total RMS signal level for the measurement selected across the current frequency span BW and the frequency displayed is that of the signal with the maximum peak The signa...

Page 55: ...kHz Selective measurements are made at the current centre frequency by pressing the key followed by the f3 soft key and then choosing the BW Alternatively the desired Centre Frequency can be entered...

Page 56: ...r keys toggles between the spectral and numerical format displays When a Distortion function is active during spectrum displays the marker is automatically set to the highest peak displayed or for SFR...

Page 57: ...MS value of the sum of all other spectral components excluding all harmonics in the current frequency span Press the f4 key to measure the Signal to Noise and Distortion ratio S ND The ratio of the RM...

Page 58: ...he desired number of harmonics to include in the calculation To view the harmonics or noise in more detail use the VertOffset setting found by pressing the key If the AutoRange setting is LVL BW the L...

Page 59: ...function and return to displaying just the level and frequency of the signal select Noise To view the spectrum display of the distortion press the key See the preceding section on Distortion Spectrum...

Page 60: ...Simultaneously the LT51 measures the level at each sweep frequency at RTX and displays the results press the key and then f3 to select Return Loss The following settings are relevant to Return Loss me...

Page 61: ...displays the cross talk measured at the near end of the pair connected to the RTX terminals The LT51 transmits either a single tone or sweeps over the selected frequency span at 0 dBm on an adjacent...

Page 62: ...he impedance always terminated set Sweeping configuration for swept or single SINE measurements The following settings are fixed for the test and cannot be altered the impedance is always terminated T...

Page 63: ...RTXa b terminals is continuously monitored and displayed on the LCD The AC voltage displayed is the true RMS value of the signal detected at the selected RTX terminals It does not include any DC comp...

Page 64: ...51 is configured as Off Hook the loop voltage measurement is made across the selected Zrtx termination and the loop current is calculated and displayed Otherwise no loop current measurement is made NO...

Page 65: ...the RTXa b connector terminals in The internal bridge network with a reference of 75 is always used to measure the impedance and provides adequate accuracy for all frequencies from 1 kHz to 500 kHz pr...

Page 66: ...ates a hand shaking sequence to connect to a remote LT51 tester The pair to be tested must be connected between the RTXa b terminals of the local and remote LT51 testers After successfully connecting...

Page 67: ...r when pressed TX or Centre frequency non zero centre frequency is not supported The following events will close down the connection to the remote LT51 pressing the Telephone or keys timeout waiting f...

Page 68: ...ssible to enable crude remote debugging of performance issues if required For this version of the LT51 the Service parameter is limited to the Custom type only To start the Self Test sequence Press f2...

Page 69: ...saved in the LT51 non volatile memory for later up load to a PC Following completion of the self test a summary of the results are displayed in the final column of each test Column 1 Name of test to...

Page 70: ...mpedance always terminated adjust the input level range or use the auto range feature set Sweeping configuration for swept or single tone measurements set the TX frequency on the local LT51 The remote...

Page 71: ...air connected to the TX terminals by setting its Transmitter Source to OFF press the key and then f4 to select FE X Talk The following settings on the local LT51 are relevant to Far End X talk measure...

Page 72: ...t bridged tap upto 3km PVF 67 and place the marker at the start of the event displaying the distance to the event It will automatically search all ranges from the lowest to the highest and zoom the wa...

Page 73: ...fault from both ends of the cable add the distances together and either adjust the PVF or use a ratio calculation to find the position Some commonly used cables and there PVFs are listed below Cable P...

Page 74: ...e knob to move the cursor across the screen ensure that any dialog boxes are cleared by pressing the key The distance from the LT51 RTXab terminals to the event marked by the cursor is always shown ne...

Page 75: ...ther to enable sections of the displayed waveform to be examined in greater detail over the whole TDR range Toggle the f5 soft key to set Offset to Horizontal A dialog box appears with the text Horizo...

Page 76: ...ength of the test leads Open A clean or partial open will show up as a peak on the screen The cleaner the open the taller the peak A complete open will be the tallest peak other than the launch pulse...

Page 77: ...a dip followed by a peak you might suspect a bridge tap Also for a bridged tap the absolute value of the dip is always greater than the absolute value of the peak Blind spot Reflections due to faults...

Page 78: ...edly press the key until the desired position is reached To store the ID string and save the measurement press the Key If you no longer want to save the measurement press any menu or soft key The wave...

Page 79: ...st move the highlight bar to the desired test by turning the knob clockwise or anti clockwise When the desired test is selected press the f3 Show Detail soft key to display the details saved for the m...

Page 80: ...val enables measurements to be recorded over weeks Before starting the Recorder select the sampling interval by pressing the f2 soft key The options are 1s 2s 5s 10s 60s To start the Recorder press th...

Page 81: ...ailable LT51View Application on a PC with a Windows 98 2000 XP Vista or 7 OS The USB drivers may also be installed manually by downloading the required files according to your OS from the FDTI website...

Page 82: ...oad tab in the main window of the application In the displayed combo box choose either Graph Results or DMM Results The list of saved measurements is displayed beneath the combo box To view a particul...

Page 83: ...ytes CMD D1 D2 D3 D4 Upon successful reception of the 5 byte command the LT51 will respond by returning an ACK 0x99 byte OR data byte s NOTE The LT51 will wait until it receives 5 bytes This can lead...

Page 84: ...EASMODE 0x00 0x20 LEVSPCTM 0x21 PSD 0x23 IPNOISE 0x26 TDR 0x28 OSB 0x30 NEXT Loss 0x31 FEXT 0x32 ILOSS 0x34 RLOSS 0x38 LCL 0x41 VOLTAGE 0x43 TRACETONE 0x47 R C 0x73 MAGZ TERMINALS 0x02 0x00 a b 0x01 a...

Page 85: ...x04 3 1 kHz GAUGE 0x0E 0x00 19AWG 0 9mm 0x04 Custom AUTORANGE 0x11 0x00 OFF 0x01 LVL only 0x02 LVL BW AVERAGING 0x1C 0x00 OFF 0x01 Averaging ON 0x02 Peak Hold ON PEAKTRK 0x1E 0x00 OFF 0x01 ON DISTORTI...

Page 86: ...Freq2 Freq3 Freq4 LT51 returns 0x99 The TX Frequency is set to TxFreq Freq1 16 777 215 Freq2 65 536 Freq3 256 Freq4 Hz Example For TxFreq 2 000 000 Hz Freq1 0x00 Freq2 0x1E Freq3 0x84 Freq4 0x80 CONF...

Page 87: ...ted terminals READDATA2 the AG terminals READDATA3 the BG terminals depending on the following current measurement mode Command Mode Data READDATA1 READDATA2 READDATA3 R C R D3 256 D2 C D1 256 D0 nF I...

Page 88: ...resume operation with the existing software 4 Start the LT51View application program and select the Download Tab on the main displayed form Manually select the a43 file by pressing the Browse File but...

Page 89: ...nsmit a tone at 10 kHz 0 dBm for a period equal to the automatic switchoff time for the LT51 Thereafter the LT51 should be turned back on and the adjustment or calibration commenced Required test equi...

Page 90: ...LT51 to adjust the level displayed on the DMM to 0 00 dBm and then press the key NOTE The knob must be turned even if the default TxLevel is correct to zero the calibration constant before pressing th...

Page 91: ...Voltage Source of 50 00 V 0 05 to the RTXa b terminals with the ve terminal to the RTXb red terminal When the LT51 measurement has stabilised press the key to record the 50 0 Vdc value Connect a DC Vo...

Page 92: ...d to any loads Use the knob press to move the cursor on the LT51 to adjust the TX Frequency constant so that the frequency displayed on the DMM is 100 000 0 Hz Press the key when the reading has stabi...

Page 93: ...ter the LT51 should be configured to transmit a tone at 10 kHz 0 dBm for a period equal to the automatic switchoff time for the LT51 Thereafter the LT51 should be turned back on and the adjustment or...

Page 94: ...0 dBm 600 30 dBr 0 30 dB 40 dBm 600 40 dBr 0 30 dB 50 dBm 600 50 dBr 0 30 dB Table 8 1 Transmitter Level Response a Set the LT51 to TX RX interface mode Set the TX level to 0 0 dBm b Set the LT51 Ztx...

Page 95: ...10 dBr 0 20 dB 20 dBm 600 20 dBr 0 20 dB 30 dBm 600 30 dBr 0 30 dB 40 dBm 600 40 dBr 0 30 dB 50 dBm 600 50 dBr 0 30 dB Table 8 3 Receiver Level Response a Set the LT51 to Level Spectrum and TX RX inte...

Page 96: ...ss mode b Set the LT51 TX frequency to 10 kHz and TX level to 10 dBm c Set the LT51 RTX impedance as indicated in Table 8 6 and connect the load impedance to the RTX terminals d Check that the reading...

Page 97: ...ge Measurement a Set the LT51 to DMM AC DC Voltage mode b Ensure that the Terminals are set to AB c Connect a 30 V 50 Hz AC Source to the LT51 RTXa b terminals d Check that the LT51 displays the AC vo...

Page 98: ......

Page 99: ...H Weight 700g Power supply Battery Type 3 AA NiMH NiCd or Alkaline Battery Life 8 hours typical 2100mAh NiMH Battery Recharge Time 5 hours in LT51 AC Operation charging Ext adaptor 240Vac to 5 or 6 V...

Page 100: ...Level Range TX RX mode 120 to 30 dBm 600 75 50 Term auto ranging or manual range setting BWs see Selectivity below 25 Hz 1 74 kHz 3 1 kHz Psoph ITU 0 41 Impedance balanced Terminated 600 75 50 Bridged...

Page 101: ...EXT FEXT measurements Impedance 600 75 50 Frequency Range 200 Hz to 2 2 MHz Level range 90 to 10 dB Accuracy 1 dB Intrinsic NEXT 75 1 MHz 80 dB 2 2 MHz 70 dB Return Loss measurement Impedance 600 75 5...

Page 102: ...75 ref 1000 10 5 Signalling Voice Communication Dial Method DTMF Redial Up to last 16 digits Talk Listen built in Speaker Microphone 600 Shunt 0 to 90 mA 1 0 5 mA Ring Detector Range Meas 40 to 100 Vr...

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