高联的另一个常见基准：4410，左边多了4个1.018v，在以下连接里卖$4995，转过来：
http://www.lehmanscientific.com/calstd2.html#anchor244544guildline model 4410 portable dc voltage standard. this standard is designed for instrumentation laboratories which must maintain a knowledge of the absolute magnitude of the volt to within a few parts per million of the national standard. features: eight independent outputs, four at 10 volts and four at 1.018 volts, simple and reliable operation, low drift, low noise, minimal leakage and line coupling, easily transported, long battery backup, low temperature coefficient, and it is acceptable for national certification. the output terminals are of gold-plated copper to reduce thermal emfs and also have custom-molded insulators of very high resistance and low moisture absorption. silvered mica capacitors and high loss toroidal inductors are used to minimize rf interference. the precision resistors are wound of "evenohm" wire from a single spool on selected mica cards in a single layer. multiple resistors of a similar value are used to provide coherence of drift and temperature coefficient, even after temperature cycling. the annealing process and stress-relief after mounting ensure great stability with time and temperature. the reference modules are housed in a heavy cast aluminum oven enclosure controlled to 33 deg c. great care is taken in routing the teflon wiring to reduce temperature gradients. the multiple outputs are the most important feature since they provide greatly improved confidence. by a simple intercomparison of the four outputs, any perturbation in an output can be readily detected. in each of the four reference modules, eight precision reference elements are averaged to reduce drift, temperature coefficient and noise.
specifications: outputs: four at 10v, four at 1.018v, influence of battery voltage limit (between the limits of 11.6v and 14v): below noise level, noise (0.3 to 10hz bandwidth): less than 0.1ppm rms, annual drift (each of the eight outputs): first year- less than -3 +/- 2 ppm, second year- less than -2 +/- 2 ppm, temperature coefficient: less than +/- 0.04ppm/deg c, isolation, ac: less than 120na case to guard leakage current, leakage resistance (outputs to guard or case): greater than 10e10 ohms, operation on battery: at least 60 hours. we have two of these superior quality voltage standards in excellent used condition. each is in current calibration with calibration reports (voltages certified to 7 decimal places for the 10v outputs, and 8 decimal places for the 1.018v outputs), and nist-traceable certifications. each has a traceability book, which contains copies of the calibration certifications of each instrument used for for calibration. these units were shipped to us "hot" so the traceability is intact. excellent used condition, checked, guaranteed. price: $4995.00 each
