Schwarzbeck VUFM 1671 LCD-Display Unit For VUFM 1670

The direct reading E-field-meter VUFM 1670 uses a moving coil meter for indication, which is very practical especially when used for fast overview measurement or outside of the laboratory.

On the other hand, it is often preferred to operate the VUFM 1670 at a distance. The small meter doesn't influence the field very much and nobody is in danger because of strong fields. A fibre optical link is best choice for interconnection, because in contrast to copper wire there is virtually no influence on the field. For this reason, the VUFM 1670 has an optional fibre link interface, which can be installed in both new and used meters.

The LCD unit gives a 3-digit reading of field strength with 3 ranges according to the ranges of VUFM 1670. Low battery voltage and range overflow are indicated be a slow or fast flashing LCD colon.

The fibre optical link uses cheap and rugged plastic fibre, which is directly clamped to transmitter and receiver diodes without the need for expensive connectors. Length up to 20 meters is standard. More distance is possible with more driving power for the transmitter diode of the VUFM 1670.

The LCD unit has a built in nicad battery. Charging requires only a simple 12 V /100 mA source. A wall plug charger is available on request.

Attention: Operation of LCD-unit VUFM 1670 is only possible in combination with E-Field-Meter VUFM 1670, which determines the system parameters. The meter voltage is converted to frequency by a high end v/f converter driving the transmitting diode. A crystal controlled multistage counter in the LCDunit converts frequency into numbers. These numbers are recalculated to give the LCD field-strength indication.

Operation

Attention: Operation of LCD-unit VUFM 1670 is only possible in combination with E-Field-Meter VUFM 1670 including the optional fibre link interface, which can be installed in older units too. The interface (transmitter diode) is located on the right hand side wall (front view). There must be a plastic clamp of approx. 8 mm in diameter.

Cutting the fibre: Low cost plastic material with 2.2 mm outer diameter is required. The fibre is used without connectors. Transmitter and receiver use a special clamping technique to fix the fibre. Just cut the piece of fibre length with a sharp knife or other appropriate tool. The cut must be even and clean. The outer plastic shielding must not be longer than the active fibre in the middle. The fibre has to be protected from mechanical stress.

VUFM 1670/VUFM 1671

For the operation of the VUFM 1670 please refer the operation manual. The optional fibre link interface consumes additional 5-7 milliamps from the battery and by that has to be considered as main consumer. Use of high quality batteries is recommended.

Operation

To connect both units to the fibre, unscrew the plastic clamp by turning it to the left (ccw) Insert one end of the fibre carefully until resistance occurs. Then turn the plastic clamp carefully to the right (cw). Stop turning when the fibre is kept well in the clamp. Do not turn too strong because this could damage the clamp. Now switch ON the VUFM 1670. Choose appropriate measuring range. Read the field-strength on the moving coil meter. Now switch ON the VUFM 1671. Choose the same measuring range. The field-strength measurement now appears on the LCD.

Low Battery voltage and range overflow

The colon included in the middle of the LCD is used for that. It flashes slowly when battery voltage drops below 5 volts. The battery then is nearly discharged and needs charging. There is still some time in spare to complete your measurement with full precision. Fast flashing of the colon stands for overflow of the measuring ranges 5 V/m, 30 V/m and 300 V/m. In this case the measurement is wrong

Battery operation

Five nicad batteries Type AA, 800 mAh are included in the VUFM 1671. When charged completely this serves for 70 to 80 hours of operation. In the real life, this charge is not always completely available. One reason is that often the battery is not completely empty before recharging. There are many attempts to fix the problem, but every day experience with rechargeable battery equipment shows, that still the lifetime is limited.

The VUFM 1671 uses the simple constant current charging. Using a 12 volts source, charging is completed within 14 hours. There are no special requirements to this source. Simple wall plug power supplies will do the job. When battery lifetime comes to the end, low cost replacement will always be possible.