DF1641A function generator

My new function generator ( bought second-hand at the start of January 2014 on a Belgian site for € 88 including postage! ) Which now replaces the old one I had built on an XR2206 base in the early 1980s.

This is the DF1641A model, without manufacturer's mark. While searching on the internet, I found a Velleman DVM20FGC which looks a lot like him and has almost the same characteristics, but no diagram for either one or the other ... not found ( if anyone has it, I would like a copy because the one I have is almost unusable .... )

image of the DF1641A function generator

When I opened it to see what condition it was in, I was very surprised by its good general condition on the one hand, but also by its manufacturing quality, although in view of the identification label on the socket. The food has a possibly Asian annotation.

image of the interior view of the DF1641A function generator

The assembly is neat, and all integrated circuits are classic CMOS models, not even the shadow of an erased marking as is often their habit!

Obviously I hastened to test it in its last entrenchments, and it is quite faithful ... the only small problem is that the duty cycle in pulse mode varies a little according to the frequency. Well, after all, it's not a Schlumberger either ... that's the only complaint!
Its use quickly becomes intuitive, and it remains a very good measuring device for a personal laboratory.
You can compare below, the precision of the 2 displays is quite correct for a selected frequency of 2MHz ( in sinusoidal mode ).

comparative image of the generator with my frequency meter at 2 MHz

Technical specifications :

1. Sine, square, triangle, positive & negative pulses, rising & falling ramp
waveforms 2. Frequency range 0.2Hz ~ 2MHz in 7 steps
         → Values ​​that I measured with the oscilloscope: 24mHz ~ 2.24MHz ( without noticeable degradation of the signal, sinusoidal in this case )
3. Rise / fall time (square wave) <100ns
4. Sinusoid shape:
         Distortion <1% between 10Hz ~ 100KHz
                        <2% between 100KHz ~ 200KHz
         Frequency response : 0.2Hz ~ 200KHz ± 5%
                                            200Hz ~ 2MHz ± 10%
5. TTL output: High level> 2.4V, Low level <0.4V, Rise time <40ns
6. Output:
         Impedance 50Ω ± 10%
         Amplitude> 20Vp-p (without load)
         Attenuator: 20dB, 40dB, 60dB, with an error of ± 0.5dB (f <200 KHz) 7.DC
offset from 0 to ± 10V, continuously adjustable (without load)
8. Symmetry adjustment range: 80:10 ~ 10:80
9. Frequency counter
         Measuring range 1Hz ~ 10MHz Input
         impedance ≥ 1MΩ /
         20pF Sensitivity 50mV
         Resolution: 100Hz, 10Hz, 1Hz, 0.1Hz in 4 steps
         Entry max. 150V (AC + DC) (with attenuator)
         Input attenuation 20dB
         Measurement error ≤ 3 x 10 -5 ± 1 digit
10. VCF input
         Input voltage 0V to 5V ± 10% DC, and reverse
         VCF ratio max. 1000: 1
11. Power source 220V ± 10% / 50Hz ± 2Hz, 10VA
12. Ambient conditions:
         Temperature 0 ~ 40 ° C
         Max. RH90%
         Atmospheric pressure 100 ± 4kPa
13. Dimensions (Length x Width x Height) 310 x 230 x 90mm
14. Weight 2kg 

PDF copy of the user manual ( with the diagram! ) Supplied with my device (in English) pdf3

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VCF controller for function generator

DSC 13432 [320x356px] shadow

What interest will you tell me?
What can it be used for?

The answer is very simple, well ... maybe not that much in the end ...
If your generator is equipped with an input[ VCF 1 ], then you will be able to control it very finely, for example using a microcontroller system equipped with a DAC converter ( D igtal A nalogic C onverter), clearly a digital / analog converter.
It goes without saying that if your GBF does not have this VCF input, then this accessory will be of no use to you!

Read more: VCF controller for function generator

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XR2206 base function generator

My function generator based on an XR2206, a little old, certainly, but very complete:

- Bandwidth from 0.1Hz to 1MHz (it's a BF gen, eh !!!)
- An 'AUDIO' knob which allows you to quickly switch from 20Hz to 20KHz
- Sine, Triangle, Square (with the added bonus of a divider / 10), Variable width pulses in 5 calibers (100ns to 10ms, positive or negative please !!!)
- Offset
adjustment - Peak adjustment up to 15V (there is still square)
- Output attenuator in several calibers, also with the possibility of isolating the output signal without disconnecting the probe ...
- Signal output on BNC (2, it is practical to also connect the frequency meter), DIN 5 pins and 2 CINCH (and yes, I was doing audio with ...)

The machine still dates from 1985 .... this explains its slightly 'weathered' appearance ...

image of the Function generator (base XR2206)

I reconstructed the diagram that I used during its construction:

diagram of my function generator ...

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