从机械式电位器升级到数字电位器

表 1. 数 字 电 位 器 与 机 械 式 电 位 器Feature Digital Pot Mechanical PotResolutionCommon-modelimitationsUnpoweredoperationDurabilityEnvironmentalconcerns32 to 256 steps are available at this time.This is presently limited to the power-supplyrails.This only functions when power is applied tothe device.The number of adjustment cycles is infinite,though nonvolatile devices may haveEEPROM-write limitation.Generally, these are very durable.Theoretically, this is infinite, though limited bythe skill level of the pot adjuster.This is limited to the breakdown voltages of thewiper/dielectric.These are functional without power, thoughutility may be limited.The number of adjustment cycles is finite, anddepend on the manufacturer/design.Depending on the design, some are verysusceptible to vibration, shock, humidity, andpressure.Setting retentionThe setting is retained without power. MoreThe setting is retained with the use of either permanent retention can be obtained by the useexternal or included EEPROM/flash memory. of a glue dab, which is difficult to remove forsubsequent adjustments.AdjustmentprocedureIn-use potadjustmentA 2-or 3-wire serial digital interface typicallyallows a MCU (or user) to adjust the pot.Also available are increment/decrementinterfaces that do not require MCUintervention.The MCU or user can adjust the pot asdesired during operation. This can be helpfulin automatically adjusting references,thresholds, etc.Typically a screwdriver is used to adjust the potuntil the desired set point is read on a voltmeteror similar.If the set screw is not glued, a screwdriver maybe used to adjust the pot manually.Scaling Linear and log are available. Linear and log are available.TemperaturecorrectionCostSeveral digital pot designs include atemperature sensor and NV memory toprovide a lookup-table-adjusted pot outputover temperature.The cost of the pot, plus the savings fromeliminating a manual adjustment procedureand from lower rework/lower warranty repaircost, results in an overall cost savings.Temperature-based adjustment is not possible.Mechanical pots are inexpensive. However, thetotal overall cost will be higher due to the laborneeded to make the adjustment, the possibilityof adjustment error, and the cost of warrantyrepairs.结 论几 乎 在 所 有 应 用 中 , 用 数 字 电 位 器 替 代 机 械 式 电 位 器 都 能 够 改 进 最 终 产 品 , 有 利 于 降 低 总 体 方 案 的 成 本 ,

提 高 生 产 流 程 的 可 靠 性 和 稳 定 下 。 另 外 一 个 好 处 是 , 利 用 软 件 可 以 实 现 系 统 的 自 动 调 节 、 设 置 。 是 系 统 更加 灵 活 、 功 能 更 广 泛