Morris Instruments Inc.

1382 McMahon Ave., Ottawa, Ont., Canada K1T 1C3
tel: (613) 523-7448
e-mail: morris-instruments@rogers.com


Model 405NV and 505NV R.F. Sweeper User Manual

ROM version 950404 to 950420 and SPC405.

Table of Contents

  1. Precautions
  2. Sweeper Overview
  3. Battery Charging
  4. Operations
  5. User Maintenance
  6. Troubleshooting
  7. Specifications
  8. Warranty
  1. Precautions
  2. Sweeper Overview (Values in parenthesis apply to the model 505NV)

    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:

    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 165 to 405 MHz (205 to 505MHz) in 100kHz steps, and a divider section which can divide the output of the PLL section by successive powers of two up to 64. Thus the total frequency range is 2.6 to 405MHz (3.2 to 505MHz). The step size is finer in the lower ranges due to the division. (See specifications.)

    The synthesizer output level is controlled by an automatic levelling circuit which may be set by the manual level adjustment on the side of the unit. 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. Unlike nickel-cadmium batteries, the sealed lead acid battery should never be totally drained as this will shorten the life, therefore it is important to recharge the battery as soon as the low battery indication flashes on the screen. (see fig. 2 below)

    fig. 2

    To recharge the battery simply plug the charger into the jack on the side of the unit and then plug in the AC line to the charger. 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 AC line to the charger and then unplug the charger from the sweeper. The charging circuit has been set up 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 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 contains a transformer and so it is highly magnetic 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. 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. at (613) 523-7448 in the case of more serious difficulties. We will be glad to help you. Our e-mail address is: morris-instruments@rogers.com

  7. Specifications
  8. Warranty

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


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Paul Morris 2010-02-02

morris-instruments@rogers.com