Morris Instruments Inc.

1382 McMahon Ave., Ottawa, Ont., Canada K1T 1C3
tel: (613) 523-7448

R.F. Sweeper User Manual

Models: 405NV+, 505NV+, 610NV+, 710NV+, 810NV+, and MX

ROM version 971201 to 120229.

Table of Contents

  1. Precautions
  2. Sweeper Overview
  3. Battery Charging
  4. Operations
  1. Precautions
  2. Sweeper Overview

    This product has been developed specifically for tuning NMR probes, although it may also find application in other areas of RF design, in particular scalar analysis of one and two port devices. Important features include:

    A simplified block diagram of the sweeper is shown in fig. 1.

    fig.1 Block Diagram

    The CPU section contains the microprocessor, RAM, ROM, and the analog to digital converter (ADC). The microprocessor receives commands from the keypad, drives the display panel, and loads the RF synthesizer.

    The synthesizer consists of a phase locked loop section which generates frequencies from 165-405, 205-505, 250-610, 300-710, 350-810, 450-1010 MHz, depending on the model, in 50kHz steps (100kHz steps for ROM versions 980101 and earlier), and a divider section which can divide the output of the PLL section by successive powers of two up to 128. Thus the total frequency range is 1.3 to 405 MHz for the 405NV+ and 1.6 to 505, 2.0 to 610, 2.4 to 710, 2.7 to 810, or 3.5 to 1010 MHz for the 505NV+, 610NV+, 710NV+, 810NV+, and MX. The step size is finer in the lower ranges due to the division. (See specifications.)

    R.F. output level is controlled by an automatic levelling circuit (ALC) which may be set by the manual level adjustment on the side of the unit or by a digital control from the CPU. (The two control voltages are multiplied together and the result used to control the ALC.) The switch between the two BNC connectors allows the synthesizer output to be sent directly to the RF OUTPUT port, or to be applied to the integral tuning bridge. With the switch set to the tuning bridge position, a device to be matched to 50 ohms may be connected to the TUNING BRIDGE port for adjustment. When the switch is set to the RF OUTPUT position then the other port becomes a 50 ohms RF detector. This allows tuning of two port devices such as filters.

  3. Battery Charging

    The rechargeable battery is of the sealed lead acid type, chosen for its non-magnetic properties and its standby characteristics. The battery should never be deep discharged, therefore it is important to recharge the unit as soon as the battery indicator flashes on the screen (see fig. 2 below), or within 60 days, whichever comes first.

    fig. 2

    As of ROM revision 20061001 the battery level indicator shows the approximate amount of charge remaining in the battery during discharge. It should always indicate full while charging. Earlier versions simply indicated the battery to be OK or flashed a LOW warning. In either case the indicator flashes when the battery needs recharging.

    To recharge, simply plug the charger into the jack on the side of the unit and then plug the charger into the AC. The charging rate is much faster if the unit is switched off than if it is on, although the unit may be operated indefinitely while connected to the charger. An overnight charge will completely recharge the battery. When charging is complete, unplug the charger from the AC and then unplug the charger from the sweeper. The charging circuit has been set for cyclic as opposed to standby use, so that for optimum battery life, the charger should be turned off and disconnected once a full charge has been reached. Operating time on a full charge is at least 3 hours.

    If the low battery indication is showing on the screen or if the battery is so low that the unit will not come on at all, then switch it off, and charge the battery as stated above, after 5-10min you may turn the unit on while charging although this will increase the time required to reach full charge.

    The charger itself may contain magnetic components and must NEVER be brought into the fringe field of NMR magnets!

  4. Operations
  5. User Maintenance

    Generally very little is required in the way of maintenance for your sweeper. The battery should be fully charged before storing the unit for an extended period of time, and it should be recharged at least every 90 days. The recommended temperature range for operation or storage is 10° to 25°C. The connectors should be kept clean, especially the TUNING BRIDGE / DETECTOR port as a poor connection here will affect the readings and may cause radio frequency emissions. An occasional spray of zero residue electronic contact cleaner into the BNC connectors, the port selection slide switch, the power ON-OFF switch, and the D.C. power jack will help keep these functioning properly. Avoid leaving the unit in direct sunlight as this will degrade the performance and life of the LCD screen.

  6. Troubleshooting

    The following is a list of common problems and solutions. Please consult Morris Instruments Inc. (ph. 613-523-7448, fax 613-523-4112) in the case of more serious difficulties. We will be glad to help you. Our e-mail address is:

  7. Specifications
  8. Warranty

    All units are covered for one full year against defects in manufacture, or failure under normal use.

    The warranty period commences upon delivery of the instrument to the end user. If the failure requires replacement of user serviceable parts (for example A.C. adapter or rechargeable battery) then the transportation cost for sending those parts to the customer will be paid fully by Morris Instruments Inc. If the sweeper needs to be returned to Morris Instruments for repair of a failure that is covered by the warranty then the customer will pay transportation back to Ottawa, Canada, and Morris Instruments Inc. will pay the return cost for transportation back from Ottawa to the end customer. The customer is responsible for any customs, duties or taxes incurred in their own country, and the customer would be responsible for all the transportation costs for repairs not covered under by this warranty, such as damage due to abuse or mishandling.

    All units returned to Morris Instruments Inc. will be fully evaluated and retested at no additional cost.

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Paul Morris 2014-09-10